Question

the p.d. across a lamp is 12V. 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 1

Answer:

p.d.=12V

(a) p.d.=

chargedmoved

workdone

work done =p.d.×chargemoved=12×1=12J

Amount of electrical energy changed into heat and light =12J

(b) work done =p.d.×chargemoved=12×5=60J

Amount of electrical energy changed into heat and light =60J

(c) I=

t

Q

Q=I×t=2×10=20C

work done =p.d.×chargemoved=12×20=240J

Amount of electrical energy changed into heat and light =240J