When 4 volts e.m.f. is applied across a 1 farad capacitor, it will store energy of

8 joules

Solution:

Energy Stored in a capacitor , U = ½ CV²

where, C is the capacitance and

V is the potential difference.

Given: V = 4 V and C = 1 F

So, U = ½(1)(4)²

U = ½(16)

U = 8 J

So, the correct option is D). 8 joules