Question

A current of 9a flows throw a lamp for 10 sec if the p.D across the lamp is 5 v how much electrical energy is converted into the heat into light

Answer 1

1. V = W/Q
12 = W/1
12 = W
Work done = 12 joules

2. V = W/Q
12 = W/5
12 x 5 = W
60 = W
word done = 60 joules

3. I= Q/t
2 = Q/10
Q = 10 x 2
Q = 20 coulombs 
V = W/Q
12 = W/20
20 x 12 = W
W = 240 joules