Numerical problems based on emf and potential difference
1] If the emf of a battery is 9 V, how much energy is converted from chemical to electrical when 2 C of charge flow?
2] What is the p.d. across a resistor if 24 J of heat is produced when a current of 2 A flows through it for 10 s?
1 ] solution:
emf = energy converted from chemical to electrical per unit charge.
So energy converted = Vq = 2 x 9 J = 18 J
2 A current flows for 10 s.
Hence, Charge Q = current x time of flow = 2 x 10 C = 20 C of charge.
Potential difference(V) = W/Q = work done per unit charge = energy per unit charge = 24/20 V = 1.2 V