Unit 9 Series & Parallel CircuitsSeries & Parallel ...€¦ · • Does adding more light bulbs to...
Transcript of Unit 9 Series & Parallel CircuitsSeries & Parallel ...€¦ · • Does adding more light bulbs to...
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Name: _____________________ Date: ________Period: ___________
Unit 9Series & Parallel CircuitsSeries & Parallel Circuits
(Filled In)
Essential Questions:
• Does adding resistors to a circuit always reduce current?
• Does adding more light bulbs to a circuit always make them
less bright?
Objectives
• Draw schematic circuit diagrams for resistors in series and in parallel
• Discuss how the total current is different for the same resistors in series vs. in parallel
• Calculate the total resistance for resistors in series vs. i ll l
Slide 2
in parallel
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Vocabulary
• Series Circuit – A circuit where the current follows one path without branching
• Parallel Circuit – A circuit where the current from the battery branches one or more times.
Slide 3
1 light bulbVoltage drop across light bulb = -9VCurrent leaving the battery = 0.9A
Draw schematic below. Include voltmeter andInclude voltmeter and ammeter.
Slide 4
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2 light bulbs in series (current doesn’t branch)Voltage drop across light bulb = -4.5VCurrent leaving the battery = 0.45A (decreases)
Draw schematic below. Include voltmeter andInclude voltmeter and ammeter.
Slide 5
Opening a switch in a series circuit stops current from flowing completely
Draw schematic below. Include voltmeter andInclude voltmeter and ammeter.
Slide 6
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2 light bulbs in parallel (current branches)
1 light bulb is disconnected
Current leaving the battery is 0.9 A
Draw schematic below. Include voltmeter and ammeter.
Slide 7
2 light bulbs in parallel (current branches)
Voltage drop across each light bulb = -9V
Current leaving the battery increases to 1.80ADraw schematic below. Include voltmeter and ammeter.
Slide 8
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Practice 1
Slide 9
Voltage across two resistors in parallel is the same. One end of each resistor is at 16V, and the other end is at 0V.
Voltage = 10 VR = 2 I = ?Use V = IR, Ohm’s Law
10 2
5
V RI
I
I A
Does current always increase when you add resistors to the circuit?
• More resistors in series reduces the current leaving the battery (total current)
• More resistors in parallel increases the current leaving the b tt
ALess current
Slide 10
battery
AMore current
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Calculating total resistance of series and parallel circuit
• Series Resistors: RTotal = R1 + R2
R1 R2
• Parallel Resistors:
R
A
1 2
1 1 1
TotalR R R
Slide 11A
R1
R2
Practice: Calculate total resistance of series and parallel circuit
• Series Resistors: RTotal = R1 + R2
10 10
Calculate total resistance:
• Parallel Resistors:
A
1 2
1 1 1
TotalR R R
Slide 12A
10
10
Calculate total resistance:
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Electric Power P = IV
• Power = Current x Voltage
• More power comes from more current for the same voltage
• To increase current in a circuit, reduce resistance!(f V IR)
Slide 13
(from V = IR)
Practice 2
V = 12 VI 0 60 A
Slide 14
P = IVMore power comes from more current for the same voltage
I = 0.60 AUse P = IV
(0.6 )(12 )
7.2
P IV A V
P W
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Practice 3
Slide 15
Practice 3 – Answers (a) and (b)
Voltage across resistor = 12 VR = 10 I = ?U V IR Oh ’ L
12 10
1 2
V RI
I
I A
Slide 16
Use V = IR, Ohm’s Law 1.2I A
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Practice 3 – Answers (c)
R
Total current = 1.5 AHow much current goes through 10 Resistor? 1.2 A, found in (b)
Thus, the rest of the 1.5 A must be going
Slide 17
through the light bulb = 1.5A – 1.2 A = 0.3 A
12 0.3
40
V RI
R
R
Voltage across light bulb = 12 VI = 0.3AR = ?Use V = IR, Ohm’s Law
Practice 3 – Answers (d)
R
Light bulb and resistor in series looks like this:
Slide 18
In series, the total resistance of the circuit increases.Thus, the total current leaving the battery decreases.
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Practice 4
Slide 19
Practice 4 - Answers
W
X
Y Z
S1
S2 F1
S1F1
Slide 20
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Practice 5
Slide 21
Practice 5Answer (a)
a) I = ?V=20V
Switch connected to X makes this circuit
Two 5 resistors in series
R = 5 + 5 = 10
20 10
2
V RI
I
I A
Slide 22
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Practice 5Answer (b)
b) I = 2 AV=20V
Switch connected to X makes this circuit
Two 5 resistors in series
(2 )(20 ) 40P IV A V W
Slide 23
Practice 5Answer (c)
Switch connected c) Placing the fuse at T will protect the circuit regardless
to Y and passes the current through U
12 and 5resistors in series
protect the circuit regardless of which point the switch connects to.If the fuse is at U, the fuse will only protect the circuit when switch is connected to Y.
Slide 24
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Practice 5Answer (d)
c) The most warmth is generated by the largest
Switch connected to W
3 and 3resistors in series
generated by the largest current (P = IV).The smallest total resistance is when the switch is connected to W.Smallest resistance generates the largest current.
Slide 25
Practice 6
V = 12 VI = 5 AUse P = IV
(5 )(12 )
60
P IV A V
P W
Slide 26
In series, resistors add like this RTotal = R1 + R2
Removing one resistors reduces the total resistance and increases current. 10 10
A
V = 120 VI = 1.5 AUse P = IV
(1.5 )(120 )
180
P IV A V
P W