LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference...

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LCHS Physics LCHS Physics Mark Ewoldsen, Ph.D. Mark Ewoldsen, Ph.D.

Transcript of LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference...

Page 1: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

LCHS PhysicsLCHS PhysicsMark Ewoldsen, Ph.D.Mark Ewoldsen, Ph.D.

Page 2: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

DefinitionsDefinitions

• VoltageVoltage: Electric Potential or Potential : Electric Potential or Potential Difference (Energy added or used)Difference (Energy added or used)– V (volts) = Joules/Coulomb V (volts) = Joules/Coulomb

– One volt = one coulomb of charge gains One volt = one coulomb of charge gains or loses one joule of energyor loses one joule of energy

Page 3: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the difference between E and V?What is the difference between E and V?

• E is the voltage supplied by a batteryE is the voltage supplied by a battery

• V is the voltage measured across a resistorV is the voltage measured across a resistor

Page 4: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

BatteriesBatteries• Positive and Negative terminals Positive and Negative terminals

– electrons leave negative terminalelectrons leave negative terminal

• Batteries use a chemical reaction to create Batteries use a chemical reaction to create voltagevoltage

• Construction: Two different metals and AcidConstruction: Two different metals and Acid– e.g. Copper, Zinc, and Citrus Acide.g. Copper, Zinc, and Citrus Acid

– e.g. Lead, Lead Oxide, Sulfuric Acide.g. Lead, Lead Oxide, Sulfuric Acid

– e.g. Nickel, Cadmium, Acid Pastee.g. Nickel, Cadmium, Acid Paste

Page 5: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.
Page 6: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

DefinitionsDefinitions

• CurrentCurrent: Flow of electric charge: Flow of electric charge– I (amps) = Q/t = Coulombs/secondI (amps) = Q/t = Coulombs/second

– Higher current increases heat due to more Higher current increases heat due to more collisions of ‘free’ electrons with atomscollisions of ‘free’ electrons with atoms

Page 7: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Effect of Currents on the BodyEffect of Currents on the Body

• 0.001 A can be felt0.001 A can be felt

• 0.005 A is painful0.005 A is painful

• 0.010 A0.010 A causes involuntary muscle causes involuntary muscle contractionscontractions

• 0.015 A causes loss of muscle control0.015 A causes loss of muscle control

• 0.070 A can be fatal if the current last for more 0.070 A can be fatal if the current last for more than 1 second than 1 second

Page 8: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Speed of Electrons in CircuitSpeed of Electrons in Circuit

• Light goes on ‘instantly’ when switch turned onLight goes on ‘instantly’ when switch turned on– Electrons do not move at speed of lightElectrons do not move at speed of light

• c = 3 x 10c = 3 x 108 8

• Electrons – 6 x 10Electrons – 6 x 1055 m/s in random directions m/s in random directions

– Signal (energy) moves at speed of light due to electric Signal (energy) moves at speed of light due to electric energy fieldenergy field

• Wire acts as pipe to guide electric fieldWire acts as pipe to guide electric field

• Electrons in circuit do not come from battery but Electrons in circuit do not come from battery but are from the wireare from the wire

Page 9: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

DefinitionsDefinitions• ResistanceResistance: : measure of a material’s ability measure of a material’s ability

to resist the flow of of electronsto resist the flow of of electrons– ΩΩ (ohms) = J-s/C (ohms) = J-s/C22

– Conductor – low resistanceConductor – low resistance• materials with free electronsmaterials with free electrons• e.g. copper, aluminum, gold, most metalse.g. copper, aluminum, gold, most metals

– Insulator – high resistanceInsulator – high resistance• materials with no free electronsmaterials with no free electrons• e.g. glass, plastics, ceramics, woode.g. glass, plastics, ceramics, wood

Page 10: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

DefinitionsDefinitions• ResistanceResistance

– Increases with length Increases with length – L– L – Decreases with cross area Decreases with cross area – A – A – ResistivityResistivity – – ρρ

• material material dependentdependent • temperature dependenttemperature dependent

R = R = ρLρL AA

Page 11: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

DefinitionsDefinitions

• PowerPower is the rate energy is converted is the rate energy is converted into another forminto another form– Resistors transform electrical energy into Resistors transform electrical energy into

light, mechanical or heat energylight, mechanical or heat energy

• Equation for Power:Equation for Power:P = I V P = I V

(Watts) – Joules/second(Watts) – Joules/second

Page 12: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

DefinitionsDefinitions

AAmmeterAmmeter: measures amp(ere)s: measures amp(ere)s

BatteryBattery: Source of energy: Source of energy

ResistorResistor: Removes energy: Removes energy

VVoltmeterVoltmeter: measures volt(age): measures volt(age)

WiresWires::

Page 13: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Reading a Voltmeter Reading a Voltmeter

Page 14: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Reading a Ammeter Reading a Ammeter

Page 15: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Making CircuitsMaking Circuits

Page 16: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Making CircuitsMaking Circuits

A

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Making CircuitsMaking Circuits

A

V

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Making CircuitsMaking Circuits

A

V

V

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V

A

How many batteries?How many batteries?

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V

A

How many ammeters?How many ammeters?

Page 21: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

V

A

How many voltmeters?How many voltmeters?

Page 22: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

V

A

How many light bulbs?How many light bulbs?

Page 23: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Ohm’s Law:Ohm’s Law:V = I RV = I R

V = voltage, I = current, R = resistanceV = voltage, I = current, R = resistance

For a given voltage, as the resistance goes up, For a given voltage, as the resistance goes up, the current will go downthe current will go down

OR

If the resistance is less, the current is moreIf the resistance is less, the current is more

Page 24: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Ohm’s LawOhm’s Law

V

A

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Ohm’s LawOhm’s Law

V

A

Page 26: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Constant VoltageConstant Voltage• For a given pressure on a car’s acceleratorFor a given pressure on a car’s accelerator

– Voltage or energy inputVoltage or energy input

• By increasing the steepness of a hillBy increasing the steepness of a hill– Changing resistanceChanging resistance

• The car’s speed will go downThe car’s speed will go down– Decrease the current or ampsDecrease the current or amps

Page 27: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Turned on

When light is first turned onWhen light is first turned on• Filament is coldFilament is cold

– The resistance is low andThe resistance is low and– since V = IR, current is highsince V = IR, current is high

• High current means filament is more likely High current means filament is more likely to burn outto burn out

Page 28: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Ohm’s Law:Ohm’s Law:V/I = RV/I = R

V = voltage, I = current, R = resistanceV = voltage, I = current, R = resistance

For a given resistance, as the voltage For a given resistance, as the voltage goes up, the current goes upgoes up, the current goes up

Page 29: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Ohm’s Law – Set ResistanceOhm’s Law – Set Resistance

A

V

A

V

A

V

A

V

Page 30: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

http://www.physics.udel.edu/wwwusers/watson/scen103/98w/note0105.html

Page 31: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

In a simple one resistor circuit, what is In a simple one resistor circuit, what is the Resistance if the Voltage is 12-V and the Resistance if the Voltage is 12-V and

Current is 3-A?Current is 3-A?

Page 32: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

In a simple one resistor circuit, what is In a simple one resistor circuit, what is the Resistance if the Voltage is 120-V the Resistance if the Voltage is 120-V

and Current is 5-A?and Current is 5-A?

Page 33: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

In a simple one resistor circuit, what is In a simple one resistor circuit, what is the Voltage if the Resistance is 12-the Voltage if the Resistance is 12- and and

Current is 3-A?Current is 3-A?

Page 34: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

In a simple one resistor circuit, what is In a simple one resistor circuit, what is the Voltage if the Resistance is 3-the Voltage if the Resistance is 3- and and

Current is 17-A?Current is 17-A?

Page 35: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

In a simple one resistor circuit, what is In a simple one resistor circuit, what is the Current if the Resistance is 3-the Current if the Resistance is 3- and and

Voltage is 17-V?Voltage is 17-V?

Page 36: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

In a simple one resistor circuit, what is In a simple one resistor circuit, what is the Current if the Resistance is 3-the Current if the Resistance is 3- and and

Voltage is 120-V?Voltage is 120-V?

Page 37: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series CircuitSeries Circuit

Page 38: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Series CircuitSeries Circuit

1.1. Determine total E (V from battery)Determine total E (V from battery)2.2. Find the total Resistance Find the total Resistance

RRT T = R= R11 + R + R2 2 + R+ R33 … …

3.3. Determine IDetermine ITT by by

I = VI = VTT/R/RTT

3.3. Since I is constant in a series circuit, find Since I is constant in a series circuit, find V (energy used) by each resistor using V (energy used) by each resistor using

V = IV = ITTRR

Page 39: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Series CircuitSeries Circuit

1.1. Determine E (V from battery)Determine E (V from battery)

Page 40: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V12 V

1 Ω2 Ω

3 Ω

Page 41: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Series CircuitSeries Circuit

1.1. Determine E (V from battery)Determine E (V from battery) - 12V- 12V2.2. Find the total ResistanceFind the total Resistance

RRT T = R= R11 + R + R2 2 + R+ R33 … …

Page 42: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V

1 1 ΩΩ2 2 ΩΩ

3 3 ΩΩ

6 6 ΩΩ = = 3 3 ΩΩ + + 2 2 ΩΩ + + 1 1 ΩΩ

Page 43: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Series CircuitSeries Circuit

1.1. Determine E (V from battery)Determine E (V from battery) - 12V- 12V

2.2. Find the total Resistance - Find the total Resistance - 6 6 ΩΩ

Page 44: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Series CircuitSeries Circuit

1.1. Determine E (V from battery)Determine E (V from battery) - 12V- 12V

2.2. Find the total Resistance Find the total Resistance - - 6 6 ΩΩ

3.3. Determine IDetermine ITT by I by ITT = V = VTT/R/RTT

2 A2 A = 12 V/ 6 = 12 V/ 6 ΩΩ

Page 45: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Series CircuitSeries Circuit

1.1. Determine E (V from battery)Determine E (V from battery) - 12V- 12V

2.2. Find the total Resistance Find the total Resistance - - 6 6 ΩΩ

3.3. Determine that IDetermine that IT T = = 2 A2 A

4.4. Since I is constant in a series circuit, find Since I is constant in a series circuit, find V (energy used ) for each resistor using V (energy used ) for each resistor using V = IV = ITTRR

Page 46: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V

1 Ω2 Ω

3 Ω

2V2V = 2A * 1 = 2A * 1ΩΩ4V4V = 2A * 2 = 2A * 2ΩΩ

6V6V = 2A * 3 = 2A * 3ΩΩ

1212V = V = 6V6V + + 4V4V + + 2V2V

Page 47: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series CircuitSeries Circuit• Current is the same at all points Current is the same at all points

I = II = I11 = I = I22 = I = I33 = I = I44

• Volt is divided among all the resistorVolt is divided among all the resistor

E = VE = V11 + V + V22 + V + V33

• Resistance accumulatesResistance accumulates

R = RR = R11 + R + R22 + R + R33

Page 48: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V12 V

1 Ω4 Ω

3 Ω

Page 49: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the total Resistance?What is the total Resistance?

12 V12 V

1 Ω4 Ω

3 Ω

Page 50: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the total Resistance? 8 What is the total Resistance? 8 ΩΩWhat is the current leaving the Battery?What is the current leaving the Battery?

12 V12 V

1 Ω4 Ω

3 Ω

Page 51: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the total Resistance? 8 ΩWhat is the total Resistance? 8 Ω

What is the current leaving the Battery? 1.5AWhat is the current leaving the Battery? 1.5A

What is the voltage used by the 1-What is the voltage used by the 1- resistor? resistor?

12 V12 V

1 Ω4 Ω

3 Ω

Page 52: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the total Resistance? 8 ΩWhat is the total Resistance? 8 Ω

What is the current leaving the Battery? 1.5AWhat is the current leaving the Battery? 1.5A

What is the voltage used by the 4-What is the voltage used by the 4- resistor? resistor?

12 V12 V

1 Ω4 Ω

3 Ω

Page 53: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the total Resistance? 8 ΩWhat is the total Resistance? 8 Ω

What is the current leaving the Battery? 1.5AWhat is the current leaving the Battery? 1.5A

What is the voltage used by the 3-What is the voltage used by the 3- resistor? resistor?

12 V12 V

1 Ω4 Ω

3 Ω

Page 54: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Parallel CircuitParallel Circuit

Page 55: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E2.2. Find the total Resistance Find the total Resistance

1/R1/RT T = 1/R= 1/R11 + 1/R + 1/R2 2 + 1/R+ 1/R33 … …

3.3. Determine IDetermine ITT leaving battery by leaving battery by

IITT = V = VTT/R/RTT

4.4. Since V is constant for each part of a parallel circuit, Since V is constant for each part of a parallel circuit, find I through each resistor using find I through each resistor using

I = V/RI = V/R

5.5. Check to verify that Kirchhoff’s Law is trueCheck to verify that Kirchhoff’s Law is true

Page 56: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

1 Ω

2 Ω

12 V

Page 57: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E 12 V12 V

Page 58: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E

2.2. Find the total Resistance Find the total Resistance

1/R1/RT T = 1/R= 1/R11 + 1/R + 1/R2 2 + 1/R+ 1/R33 … …

Page 59: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

1 Ω

2 Ω

1/R1/RT T = 1/1= 1/1ΩΩ + 1/2 + 1/2ΩΩ1/R1/RT T = 3/2= 3/2ΩΩ

12 V

RRT T = = 22ΩΩ/3/3

Page 60: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E

2.2. Find the total Resistance Find the total Resistance

1/R1/RT T = 1/R= 1/R11 + 1/R + 1/R2 2 + 1/R+ 1/R33 … …

RRT T = 2= 2ΩΩ/3/3

Page 61: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E

2.2. Find the total Resistance Find the total Resistance

1/R1/RT T = 1/R= 1/R11 + 1/R + 1/R2 2 + 1/R+ 1/R33 … …

3.3. Determine IDetermine IBB leaving battery by leaving battery by

IIBB = V = VBB/R/RTT

IIBB = 12V / 2 = 12V / 2ΩΩ/3 /3 oror 12V x 3/2 12V x 3/2ΩΩ

IIBB = 18A = 18A

Page 62: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

1 Ω

2 Ω

12 V

IIBB = 18A = 18A

Page 63: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E

2.2. Find the total Resistance Find the total Resistance

1/R1/RT T = 1/R= 1/R11 + 1/R + 1/R2 2 + 1/R+ 1/R33 … …

3.3. Determine IDetermine ITT leaving battery by leaving battery by

IITT = V = VTT/R/RTT

4.4. Since V is constant for each part of a parallel Since V is constant for each part of a parallel circuit, find I through each resistor using circuit, find I through each resistor using

I = V/RI = V/R

Page 64: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

1 Ω

2 Ω

12 V

I = 12V / 1I = 12V / 1Ω = 12AΩ = 12A

I = 12V / 2I = 12V / 2Ω = 6AΩ = 6A

Page 65: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Parallel CircuitParallel Circuit

1.1. Determine EDetermine E

2.2. Find the total Resistance Find the total Resistance

1/R1/RT T = 1/R= 1/R11 + 1/R + 1/R2 2 + 1/R+ 1/R33 … …

3.3. Determine IDetermine ITT leaving battery by leaving battery by

IITT = V = VTT/R/RTT

4.4. Since V is constant for each part of a parallel circuit, Since V is constant for each part of a parallel circuit, find I through each resistor using find I through each resistor using

I = V/RI = V/R

5.5. Check to verify that Kirchhoff’s Rule is trueCheck to verify that Kirchhoff’s Rule is true

Page 66: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

1 Ω

2 Ω

12 V

18A18A

12A12A

6A6A

18A18A

IIBB = 18A = 18A

Page 67: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Parallel CircuitParallel Circuit

Volt is the same at all points Volt is the same at all points

E = VE = V11 = V = V22 = V = V33

ResistanceResistance 1 1 1 11 1 1 1--- = --- + --- + ------ = --- + --- + --- R RR R11 R R22 R R33

Current accumulatesCurrent accumulates

I = II = I11 + I + I22 + I + I33

Page 68: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ

2 2 ΩΩ

20 V20 V

Page 69: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ2 2 ΩΩ

20 V20 V

What is the voltage?What is the voltage?

Page 70: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ2 2 ΩΩ

20 V20 V

What is the voltage? 20VWhat is the voltage? 20V

What is the total Resistance?What is the total Resistance?

Page 71: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ2 2 ΩΩ

20 V20 V

What is the voltage? 20VWhat is the voltage? 20V

What is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω What is the total current?What is the total current?

Page 72: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ2 2 ΩΩ

20 V20 V

What is the voltage? 20VWhat is the voltage? 20VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 20 AWhat is the total current? 20 A

What is the voltage through each What is the voltage through each resistor?resistor?

Page 73: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ2 2 ΩΩ

20 V20 V

What is the voltage? 20VWhat is the voltage? 20VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 20 AWhat is the total current? 20 AWhat is the voltage through each resistor? 20VWhat is the voltage through each resistor? 20V

What is the current through each What is the current through each resistor?resistor?

Page 74: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ2 2 ΩΩ

20 V20 V

What is the voltage? 20VWhat is the voltage? 20VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 20 AWhat is the total current? 20 AWhat is the voltage through each resistor? What is the voltage through each resistor?

20V20VWhat is the current through each resistor?What is the current through each resistor?

10A10A

Page 75: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ

3 3 ΩΩ

24 V24 V

Page 76: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ3 3 ΩΩ

24 V24 V

What is the voltage?What is the voltage?

Page 77: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ3 3 ΩΩ

24 V24 V

What is the voltage? 24VWhat is the voltage? 24V

What is the total Resistance?What is the total Resistance?

Page 78: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ3 3 ΩΩ

24 V24 V

What is the voltage? 24VWhat is the voltage? 24V

What is the total Resistance? 1.2 ΩWhat is the total Resistance? 1.2 Ω What is the total current?What is the total current?

Page 79: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ3 3 ΩΩ

24 V24 V

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 1.2 ΩWhat is the total Resistance? 1.2 Ω

What is the total current? 20 AWhat is the total current? 20 A

What is the voltage through each What is the voltage through each resistor?resistor?

Page 80: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ3 3 ΩΩ

24 V24 V

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 20 AWhat is the total current? 20 AWhat is the voltage through each resistor? 24VWhat is the voltage through each resistor? 24V

What is the current through each What is the current through each resistor?resistor?

Page 81: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ3 3 ΩΩ

24 V24 V

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 20 AWhat is the total current? 20 AWhat is the voltage through each resistor? What is the voltage through each resistor?

24V24VWhat is the current through each resistor?What is the current through each resistor?

12A12A + 8A = 20A+ 8A = 20A

Page 82: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 83: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage?What is the voltage?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 84: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24V

What is the total Resistance?What is the total Resistance?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 85: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24V

What is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω What is the total current?What is the total current?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 86: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 24 AWhat is the total current? 24 A

What is the voltage through each What is the voltage through each resistor?resistor?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 87: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 24 AWhat is the total current? 24 AWhat is the voltage through each resistor? 24VWhat is the voltage through each resistor? 24V

What is the current through each What is the current through each resistor?resistor?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 88: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 1.0 ΩWhat is the total Resistance? 1.0 Ω

What is the total current? 24 AWhat is the total current? 24 AWhat is the voltage through each resistor? What is the voltage through each resistor?

24V24VWhat is the current through each resistor?What is the current through each resistor?

4A + 8A4A + 8A + 12A = 24A+ 12A = 24A

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ

Page 89: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Complex CircuitsComplex Circuits

Page 90: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 Ω

12 V

2 Ω

2 Ω

Page 91: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion3.3. Continue until the Total Resistance for the Circuit is Continue until the Total Resistance for the Circuit is

knownknown4.4. Starting with the least complex resistor, find the Starting with the least complex resistor, find the

voltage it usesvoltage it uses5.5. Continue until the parallel portion where the Continue until the parallel portion where the

remaining voltage will used on both sides will be remaining voltage will used on both sides will be identical, Find Iidentical, Find I

6.6. Make sure Kirchhoff's Rule is followedMake sure Kirchhoff's Rule is followed

Page 92: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Find the most complex portion of the Circuit – usually part of the ParallelCircuit – usually part of the Parallel

Page 93: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ

12 V

2 2 ΩΩ

2 Ω

Page 94: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion

Page 95: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V

2 2 ΩΩ

2 2 ΩΩ

2 Ω

1/R1/RT T = 1/2= 1/2ΩΩ + 1/2 + 1/2ΩΩ1/R1/RT T = 2/2= 2/2ΩΩ

RRT T = 1= 1ΩΩ

Page 96: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion

3.3. Continue until the Total Resistance for the Continue until the Total Resistance for the Circuit is knownCircuit is known

Page 97: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V

2 2 ΩΩ

2 2 ΩΩ

2 Ω

RRT T = 2= 2ΩΩ + 1 + 1ΩΩRRT T = 3= 3ΩΩ

Page 98: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion

3.3. Continue until the Total Resistance for the Circuit is Continue until the Total Resistance for the Circuit is knownknown

4.4. Find the Current that leaves the batteryFind the Current that leaves the battery

Page 99: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V

2 2 ΩΩ

2 2 ΩΩ

2 Ω

V = IR or I = V/RV = IR or I = V/RI = 12V / 3I = 12V / 3ΩΩ

I = 4AI = 4A

, 4A, 4A

Page 100: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion

3.3. Continue until the Total Resistance for the Circuit is Continue until the Total Resistance for the Circuit is knownknown

4.4. Starting with the least complex resistor, Starting with the least complex resistor, find the voltage it usesfind the voltage it uses

Page 101: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

2 2 ΩΩ

12 V, 4A

2 2 ΩΩ

V = IRV = IRSince it is series, I = 4ASince it is series, I = 4A

V = 4A x 2 V = 4A x 2 ΩΩ

V = 8V V = 8V 2 2 ΩΩ8V8V

Page 102: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion3.3. Continue until the Total Resistance for the Circuit is Continue until the Total Resistance for the Circuit is

knownknown4.4. Starting with the least complex resistor, find the Starting with the least complex resistor, find the

voltage it usesvoltage it uses

5.5. Continue until the parallel portion where Continue until the parallel portion where the remaining voltage will used on both the remaining voltage will used on both sides will be identical, Find Isides will be identical, Find I

Page 103: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V, 4A

22Ω Ω

22Ω Ω

2 Ω8V

12V – 8V = 4V12V – 8V = 4V

I = 4V / 2I = 4V / 2Ω = 2AΩ = 2A

I = 4V/2I = 4V/2Ω = 2AΩ = 2A

4V 4V

4V4V

Page 104: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Finding V, I & R for a Finding V, I & R for a Complex CircuitComplex Circuit

1.1. Find the most complex portion of the Circuit – usually Find the most complex portion of the Circuit – usually part of the Parallelpart of the Parallel

2.2. Find the Total Resistance for that portionFind the Total Resistance for that portion3.3. Continue until the Total Resistance for the Circuit is Continue until the Total Resistance for the Circuit is

knownknown4.4. Starting with the least complex resistor, find the Starting with the least complex resistor, find the

voltage it usesvoltage it uses5.5. Continue until the parallel portion where the Continue until the parallel portion where the

remaining voltage will used on both sides will be remaining voltage will used on both sides will be identical, Find Iidentical, Find I

6.6. Make sure Kirchhoff's Rule is followedMake sure Kirchhoff's Rule is followed

Page 105: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

12 V, 4A

2 2 Ω, 4VΩ, 4V

2A + 2A = 4A2A + 2A = 4A

2A2A

2A2A

4A4A

4A4A

4A4A

2 Ω8V

2 2 Ω, 4VΩ, 4V

Page 106: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Try this!Try this!

‘Some Electrical Circuit Components and Circuits’ by Michael Condren, Professor of Chemistry, Christian Brothers University, Memphis,  TN   @ http://www.cbu.edu/~mcondren/chem415/c415_ele.ppt, 4/17/04

R6=5

R1= 5

R2=10

R5=6

R3=6R4=12

Page 107: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

R6=5

R1= 5

R2=10R5=6

R3=6R4=12

R7

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 108: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

resistors 3 and 4 are in parallelresistors 3 and 4 are in parallel

1 1 1 1 1 1 1 1 1 1 --- = --- + --- = ----- + ---------- = --- + --- = ----- + -------

RR77 R R33 R R44 66 1212

= 0.25= 0.25 -1-1

RR77 = 4 = 4

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 109: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

R6=5

R1= 5

R2=10R5=6

R7=4

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 110: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

R6=5

R1= 5

R2=10R5=6

R7=4R8

Series-Parallel CircuitSeries-Parallel Circuit

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 111: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

resistor 5 and equivalent resistance 7 are in resistor 5 and equivalent resistance 7 are in seriesseries

RR88 = R = R77 + R + R55 = (4 + 6) = (4 + 6) = = 1010

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 112: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

R6=5

R1= 5

R2=10 R8=10

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 113: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

R6=5

R1= 5

R2=10 R8=10R9

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 114: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

resistor 2 and equivalent resistance 8 in resistor 2 and equivalent resistance 8 in parallelparallel

1 1 1 1 11 1 1 1 1--- = ----- + ----- = ------- + ---------- = ----- + ----- = ------- + ------- RR99 R R22 R R88 10 10 1010

= 0= 0.2 .2 -1 -1 ; R ; R9 9 = 5= 5

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 115: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

R6=5

R1= 5

R9=5V=7.5v

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 116: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Try this!Try this!

Page 117: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage?What is the voltage?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Page 118: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24V

What is the total Resistance?What is the total Resistance?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Page 119: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24V

What is the total Resistance? 4.0 ΩWhat is the total Resistance? 4.0 Ω What is the total current?What is the total current?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Page 120: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 4.0 ΩWhat is the total Resistance? 4.0 Ω

What is the total current? 6.0 AWhat is the total current? 6.0 A

What is the voltage through each What is the voltage through each resistor?resistor?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Page 121: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 4.0 ΩWhat is the total Resistance? 4.0 Ω

What is the total current? 6 AWhat is the total current? 6 AWhat is the voltage through each resistor? What is the voltage through each resistor?

3 Ω: 18V and 6V3 Ω: 18V and 6V

What is the current through each What is the current through each resistor?resistor?

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Page 122: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

What is the voltage? 24VWhat is the voltage? 24VWhat is the total Resistance? 4.0 ΩWhat is the total Resistance? 4.0 Ω

What is the total current? 6 AWhat is the total current? 6 AWhat is the voltage through each resistor? What is the voltage through each resistor?

3 Ω: 18V and 6V3 Ω: 18V and 6V What is the current through each resistor?What is the current through each resistor?

3 Ω: 6A and 2 Ω: 3A 3 Ω: 2A 6 Ω: 1A3 Ω: 6A and 2 Ω: 3A 3 Ω: 2A 6 Ω: 1A

3 3 ΩΩ

6 6 ΩΩ

24 V24 V

2 2 ΩΩ3 3 ΩΩ

Page 123: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Power• Power is the amount of energy that is transferred Power is the amount of energy that is transferred

every secondevery second

• Power is measured in wattsPower is measured in watts

P = I x VP = I x V

• PP = The power transferred by the component = The power transferred by the componentII = The current going through a component = The current going through a componentVV = The voltage across a component = The voltage across a component

• Remember that a kilowatt = 1,000 wattsRemember that a kilowatt = 1,000 watts

Page 124: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

An electric iron draws a current of An electric iron draws a current of 4A at 250V. What is its power 4A at 250V. What is its power usage?usage?

A.A. 0.0166W 0.0166W

B.B. 60W 60W

C.C. 1000W1000W

Page 125: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

A common lightbulb reads 60W, A common lightbulb reads 60W, 120V. How much current in 120V. How much current in amperes will flow through the amperes will flow through the bulb?bulb?

A.A. 7200 amps 7200 amps

B.B. 0.5 amps0.5 amps

C.C. 2.0 amps2.0 amps

Page 126: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

PracticePracticeDetermine the cost of using the following appliances for the Determine the cost of using the following appliances for the time indicated if the average cost is 9 cents/kWh.time indicated if the average cost is 9 cents/kWh.

(a) 1200W iron for 2 hours(a) 1200W iron for 2 hours

1.2 kW x (2h) x 9 cents = kWh

12.2 cents

Page 127: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

PracticePracticeDetermine the cost of using the following appliances for the time indicated if the average cost is 9 Determine the cost of using the following appliances for the time indicated if the average cost is 9 cents/kWh.cents/kWh.

(a) 1200W iron for 2 hours(a) 1200W iron for 2 hours

(b) 160W color TV for 3 hours and 30 minutes(b) 160W color TV for 3 hours and 30 minutes

1.2 kW x (2h) x 9 cents = kWh

12.2 cents

0.16 kW x (3.5h) x 9 cents = kWh

5.04 cents

Page 128: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

PracticePracticeDetermine the cost of using the following appliances for the time indicated if the average cost is 9 cents/kWh.Determine the cost of using the following appliances for the time indicated if the average cost is 9 cents/kWh.

(a) 1200W iron for 2 hours(a) 1200W iron for 2 hours

(b) 160W color TV for 3 hours and 30 minutes(b) 160W color TV for 3 hours and 30 minutes

(c) Six 60W bulbs for 7 hours.(c) Six 60W bulbs for 7 hours.

1.2 kW x (2h) x 9 cents = kWh

12.2 cents

0.16 kW x (3.5h) x 9 cents = kWh

5.04 cents

6 x .06 kW x (7h) x 9 cents = kWh

22.68 cents

Page 129: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Concept TestConcept Test

For resistors in For resistors in seriesseries, what is the same , what is the same for every resistor? R, V or I?for every resistor? R, V or I?

A.A.RR

B.B.VV

C.C.II

Page 130: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Concept TestConcept Test

For resistors in For resistors in parallelparallel, what is the same , what is the same for every resistor? for every resistor?

A.A.RR

B.B.VV

C.C.II

Page 131: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Series-Parallel CircuitSeries-Parallel Circuit

R6=5

R1= 5

R2=10R5=6

R3=6R4=12

EXAMPLE: What is the equivalent resistanceand current for the following circuit?

Page 132: LCHS Physics Mark Ewoldsen, Ph.D. Definitions Voltage: Electric Potential or Potential Difference (Energy added or used)Voltage: Electric Potential or.

Bibliography Bibliography 1. ‘Some Electrical Circuit Components and Circuits’ by Michael Condren,

Professor of Chemistry, Christian Brothers University, Memphis,  TN  @ http://www.cbu.edu/~mcondren/chem415/c415_ele.ppt, 4/17/04

2. ‘Fundamentals of Electronics,’ Dan Bruton, Professor of Astrophysics Stephen F. Austin State University @ observe.phy.sfasu.edu/courses/phy262/ lectures262, 4/17/04