Internal Resistance & EMF Quiz

Which of the following best describes electromotive force (EMF)?

• The force that moves electrons through a circuit.

• The total energy supplied per unit charge by a power source.

• The total energy lost as heat in a circuit.

• The voltage measured across a resistor.

Which statement about internal resistance is correct?

• Internal resistance increases the total voltage in a circuit.

• Internal resistance only affects current in AC circuits.

• Internal resistance causes a voltage drop inside the battery.

• Internal resistance is always zero in ideal circuits.

A battery provides 12 V EMF and has an internal resistance of 2 Ω. If the current flowing is 3 A, what is the terminal potential difference?

• 12 V

• 10 V

• 6 V

• 8 V

A battery has an EMF of 9 V and supplies a current of 2 A. If the voltage across the external circuit is 8.5 V, what is the internal resistance of the battery?

• 0.25 Ω

• 0.5 Ω

• 4.5 Ω

• 9.0 Ω

When does a circuit transfer maximum power from the power source to the load?

• When external resistance is greater than internal resistance.

• When internal resistance is greater than external resistance.

• When external resistance is equal to internal resistance.

• When there is no internal resistance.

A graph of terminal potential difference V against current I is plotted for a battery. What does the gradient of the graph represent?

• The EMF of the battery.

• The negative internal resistance of the battery.

• The total resistance of the circuit.

• The lost volts in the battery.

Why do car batteries have a very low internal resistance?

• To allow a large current flow needed to start the engine.

• To prevent the battery from heating up.

• To provide a higher EMF.

• To prevent energy loss in the circuit.

Which statement about EMF is incorrect?

• EMF is always greater than or equal to the terminal voltage.

• EMF is the energy transferred per unit charge.

• EMF is always the same as the voltage across the battery.

• EMF accounts for both useful energy and lost energy.