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14/07/2021 3:33 pm
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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?
1 Answer
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14/07/2021 3:48 pm
P.D = 12V
(a) P.d = Work done/Charge moved
Work done = p.d x charge moved
= 12 x 1 = 12 J
Amount of electrical energy changed into heat and light = 12 J
(b) Work done = p.d x charge moved
= 12 x 5 = 60 J
Amount of electrical energy changed into heat and light = 60J
(c) I = Q/t
Q = I x t
= 2 x 10 = 20 C
Work done = p.d x charge moved
= 12 x 20 = 240 J
Amount of electrical energy changed into heat and light = 240 J