Let’s solve 2 numerical problems based on emf and potential difference.

**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?

**Solutions1 ]** solution:

emf = energy converted from chemical to electrical per unit charge.

So energy converted = Vq = 2 x 9 J = 18 J

**2] **solution:

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

**[ derivation of the equation of potential difference ]**

**[ Potential difference worksheet with solved problems]**