Question: how to calculate potential difference across a bulb?
Answer: force ε: the increase in potential energy per unit charge provided by the chemical reactions in the battery. And the voltage difference across the light bulb is: ∆V = I R = (0.06 A)(20 Ω) = 1.2 V ▪If we measure the voltage difference across the battery or the light bulb, we will get 1.2 V.