When a battery is not used in a circuit, a voltmeter measure 1.492V across the terminals of the battery. When a 2.50Ω light bulb is connected to the battery, the potential difference across the terminal of the battery is 1.453V. Calculate the internal resistance of the battery

Answer 1

I = V/Rl = 1.453/2.50 = 0.5812A.
r = (1.492-1.453)/0.5812 = 0.0671 Ohms = Internal resistance.