Question 24:
The p.d. across a lamp is 12 V. How many joules of electrical energy are changed into heat and light when :
(a) a charge of 1 C passes through it ?
(b) a charge of 5 C passes through it ?
(c) a current of 2 A flows through it for 10 s ?
Lakhmir Singh Physics Class 10
Answers
The p.d. across a lamp is 12 V. How many joules of electrical energy are changed into heat and light when :
(a) a charge of 1 C passes through it ?
(b) a charge of 5 C passes through it ?
(c) a current of 2 A flows through it for 10 s ?
Answer:
Given p.d is 12 V.
(a)
when a charge of 1 C passes through
from the formula...
p.d. = work done/charge moved
work done = p.d. × charge moved
work done = 12 × 1 = 12J
so the amount of energy energy charge into the heat and light is 12J
(b)
when a charge of 5 C passes through
from the formula...
p.d. = work done/charge moved
work done = p.d. × charge moved
work done = 12 × 5 = 60J
so the amount of energy energy charge into the heat and light is 12J
(c)
I = Q/t
Q = I × t
Q = 2 × 10 = 20
Q = 20
Now from the above formula..
work done = p.d × charge moved
work done = 12 × 20 = 240J