UNIT 5

UNIT 5

ELECTRICITY

ELECTRON’S CHARGE, e-

(Units of Coulombs (C))

e- = 1.6 x 10 -19 C

A lightning strike has

about 20 -30

Coulombs of charge!

STATIC ELECTRICITY

Opposites Attract!

INSULATORS VS. CONDUCTORSInsulators (non-conductors) Conductors

Charges are stuck where you put them Charges are able to move freely &

spread out

Ex: wood, rubber, glass Ex: metals, water, human body

*Semi-conductors are

somewhere in between*

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UNIT 5

ELECTRIC FORCE

COULOMB’S LAW

ELECTROSTATIC FORCE

(Units of Newtons (N))

Distance between

particles (in m)

Charge of 2nd particle

(in Coulombs)

𝐹𝑒 = k(𝑞1 ∗ 𝑞2)

𝑑2

Charge of 1st particle

(in Coulombs)

Coulomb’s constant

k = 9 x 109 N·m2/ C2

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UNIT 5

ELECTRIC FIELDS

ELECTRIC FIELD

POSITIVELY CHARGED OBJECT

So we draw field lines radiating outward from

a positively charged object.

+

ELECTRIC FIELD

NEGATIVELY CHARGED OBJECT

So we draw field lines radiating toward a

negatively charged object.

-

UNIT 5

CIRCUITS

CURRENT

I = Current (amps, A)

V = Voltage (volts, V)

R = Resistance (ohms, Ω)

POWER

P = Power (watts, W)

V = Voltage (volts, V)

I = Current (amps, A)

EXAMPLEA light bulb in a circuit with a 12 V battery uses 24 watts.

What is the resistance of the light bulb?

EXAMPLEA light bulb in a circuit with a 12 V battery uses 24 watts.

What is the resistance of the light bulb?

G: V = 12 V

P = 24 W

U: R = ? I =?

E: I = V/R R = V/I

P = VI I = P/V

S: I = 24W / 12 V = 2 amps

R = 12 V / 2 A = 6 ohms

R = 6 ohms

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What is the total resistance of this

circuit?

12 V

1 Ω2 Ω

3 Ω

UNIT 5

SERIES

-CURRENT CONSTANT

V I R

R1 2 V 2 A 1 Ω

R2 4 V 2 A 2 Ω

R3 6 V 2 A 3 Ω

Total 12 V 2 A 6 Ω

UNIT 5

PARALLEL

-VOLTAGE CONSTANT

PARALLEL CIRCUITS

What is the total

resistance?

V I R

R1 9 V 3 A 3 Ω

R2 9 V 1.8 A 5 Ω

R3 9 V 1.5 A 6 Ω

Total 9 V 6.30 A 1.428 Ω

UNIT 5

COMBINATION

Total resistance =

Total current =

COMBINED CIRCUIT EXAMPLE

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UNIT 4

MAGNETISM

•Close together = STRONG field

•Far apart = WEAK field

•Fields are strongest at the poles

Magnetic Fields: surrounds a magnet and exerts

a magnetic force on other objects

Start

NorthEnd

South

MAGNETIC FIELDS

Earth behaves like a

large bar magnet

•North magnetic pole of

the earth is at the

physical south pole

•South magnetic pole

of the earth is at the

physical north pole

How Does a Compass Work?

To find direction of magnetic field due to a current carrying

wire, point the thumb of your right hand along the wire in

the direction of the current I.

Your fingers are now curling around the wire in the direction

of the magnetic field.

RIGHT HAND STRAIGHT WIRE RULE

When the fingers of the right-hand curl around

a solenoid in the direction of the current, the

thumb points to the NORTH POLE

RIGHT HAND SOLENOID RULE

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