2006 Section 2 Question 27

27) 5 seconds

Current (I) = Charge (Q) ÷ time (t)

I = Q ÷ t

We know charge density = charge per unit surface area

Charge density (0.25) = charge ÷ unit surface area (0.04)
Charge (Q) = 0.25 x 0.04 = 0.01 C

I = Q ÷ t

I = 2mA = 0.002 A
Q = 0.01 C
t = ?

t = (Q ÷ I) = (0.01 ÷ 0.002) = 5 seconds