When a current is in a component, the energy transferred depends on three things: the current, the potential difference across the component, and the time. They are linked by the equation energy transferred = current × potential difference × time, or E = I × V × t. Energy is in joules (J), current in amperes (A), potential difference in volts (V) and time in seconds (s).
A bigger current, a bigger potential difference or a longer time each gives a greater energy transfer. Doubling any one of them doubles the energy.
Worked example: a current of 2 A at 12 V for 30 s transfers E = 2 × 12 × 30 = 720 J. The time must always be in seconds, so 2 minutes is 120 s and the energy for 2 A at 12 V is E = 2 × 12 × 120 = 2880 J.