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Ω

OHM’S LAW

VOLTAGE, RESISTANCE, CURRENT

AND

FACTORS AFFECTING RESISTANCE

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RESISTANCE (R)

Opposition to flow of charge

Better conductors have lower resistance, by letting ______ move through them easier.

Units: Ohms Ω

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RESISTANCE

Depends on:

    • Material type: insulators vs. conductors
    • Temperature: warmer = more resistance
    • Length: longer = more resistance
    • Thickness: thinner = more resistance

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CURRENT (I)

Flow of charge = Electric Current

Measured in Amperes, or Amps (A)

Amperes measure how much charge moves per second.

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VOLTAGE (V)

Voltage measures Electric Potential

The “push” that makes electrons move.

Measured in Volts (V)

Volts = energy per charge

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OHM’S LAW

V = I • R

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Practice: When using a 1.5V battery and a 2 Ω light bulb, how much current is present?

V = 1.5V (divide both sides by 2 ohms)

R = 2 Ω

I = ? (answer = .75 Amps)

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MORE PRACTICE

Find the voltage required to move 15 amps when resistance is 3 ohms.

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Solve for the resistance in a circuit with 100A of current at 240V.

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ANSWERS

15A * 3 ohms = 45V

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240V / 100A = 2.4 ohms

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(LASERDISCS IF TIME)

V / I = Futile!