A 7 V battery is connected in series with five resistors: 0.1 Ω, 0.4 Ω, 0.5 Ω, 0.6 Ω, and 12.4 Ω. What is the current flowing through the 12.4 Ω resistor?

A wire of a given material has length l and cross-sectional area A, and its resistance is 9 Ω. Another wire of the same material has length l/3 and cross-sectional area 3A. What will be the resistance of the second wire?

If the potential difference between two points is V and charge q moves between them, the work done is _________.