Ohm's Law: voltage, current, resistance · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Ohm's Law: V = IR

Science · Energy · ages 12-13
Name ______________________   Date ____________

  1. A wire has a resistance of 5 ohms. What is the voltage needed to push 2 A through it?

    Answer: ______________

  2. A 9 V battery is connected to a resistor. The current is 0.03 A. What is the resistance in ohms?

    Answer: ______________

  3. Which factor does NOT affect the resistance of a wire?

    • Length of the wire
    • Thickness of the wire
    • Material of the wire
    • Color of the insulation

  4. If you double the resistance in a circuit while keeping the voltage the same what happens to the current?

    • It doubles
    • It halves
    • It stays the same
    • It quadruples

  5. Which unit is used to measure resistance?

    • Volts
    • Amps
    • Ohms

  6. A circuit has a voltage of 20 volts and a current of 4 amps. What is the resistance?

    • 5 Ω
    • 16 Ω
    • 24 Ω

  7. A circuit has a current of 2 amps and a resistance of 5 ohms. What is the voltage?

    • 2.5 V
    • 7 V
    • 10 V

  8. A circuit has a voltage of 9 volts and a resistance of 3 ohms. What is the current, in amps?

    Answer: ______________

  9. Priya doubles the resistance in a circuit but keeps the battery voltage the same. What happens to the current?

    • It doubles
    • It stays the same
    • It is cut in half

  10. Diego says a longer, thinner wire has less resistance than a short, thick wire of the same material. Is he correct?

    • Yes, length and thickness don't matter
    • No, longer and thinner wires have more resistance
    • Yes, but only for metal wires
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Answer key

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Ohm's Law: V = IR W1-mt_H3ZDK0EYNV-s1

  1. 10 · Use V = IR = 2 × 5 = 10 V.
  2. 300 · Rearrange V = IR to R = V/I = 9 / 0.03 = 300 ohms.
  3. Color of the insulation · Resistance depends on length thickness and material resistivity. Insulation color does not affect electrical resistance.
  4. It halves · From I = V/R if R doubles and V is constant then I becomes half.
  5. Ohms · Resistance is measured in ohms, using the symbol Ω.
  6. 5 Ω · Rearrange V = IR to solve for resistance: R = V divided by I = 20 divided by 4 = 5 ohms.
  7. 10 V · V = IR = 2 x 5 = 10 volts.
  8. 3 · Rearrange V = IR to solve for current: I = V divided by R = 9 divided by 3 = 3 amps.
  9. It is cut in half · Since I = V divided by R, doubling R while V stays fixed makes the current half as big.
  10. No, longer and thinner wires have more resistance · Longer wires and thinner wires both give charge a harder, longer path, so they raise resistance rather than lower it.
Worksheet · LightMySky