Internal Resistance

Batteries and generators add some resistance to a circuit. This resistanceis called internal resistance.

The actual voltage between the terminals of a batter is known as theterminal voltage.

The Terminal Voltage of a Battery

The car battery has an emf of 12.0 V and an internalresistance of 0.0100 Ω. What is the terminal voltagewhen the current drawn from the battery is (a) 10.0 Aand (b) 100.0 A?

(a)

(b)

Practice 2A new “D” battery has an emf of 1.5 V. When a wire of negligible resistance is connected between the terminals of the battery, a current of 28 A is produced. Find the internal resistance of the battery.

Practice 3A battery has an internal resistance of 0.012 Ω and an emf of 9.00 V. What is the maximum current that can be drawn from the battery without the terminal voltage dropping below 8.90 V?

Practice 4When a light bulb is connected across the terminals of a battery, the battery delivers 24 W of power to the bulb. A voltage of 11.8 V exists between the terminals of the battery, which has an internal resistance of 0.10Ω. What is the emf of the battery?

LabMaterials: Multi-meter, ceramic resistor, battery, wires.

What you are allowed to do: use M-meter as an A-meter and a V-meter. Direct measurement of resistance is not allowed.