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The PD across a lamp is 12V. How many joules of electric energy is changed into heat and light when:
a) a charge of 1C passes through it?
b) a charge of 5C passes through it?
c) a current of 2A flows through it for 10s?
Given: The potential difference across a lamp = 12v
a) To find: We have to find how many joules of electric energy is changed into heat and light when 1C passes through the lamp.
Solution: We know that,
$v=\ \frac{W}{ \begin{array}{l} Q\ \end{array}}$
=> Work done(W) = PD x Charge = 12 x 1 = 12J
b) To find: We have to find how many joules of electric energy is changed into heat and light when 5C passes through the lamp.
Solution: We know that,
$v=\ \frac{W}{ \begin{array}{l} Q\ \end{array}}$
=> Work done(W) = PD x Charge = 12 x 5 = 60J
c) To find: We have to find how many joules of electric energy is changed into heat and light when a current of 2A flows for 10 seconds through the lamp.
Solution: We know that,
Q = I x t
=> Q = 2 x 10 = 20C
Now,
$v=\ \frac{W}{ \begin{array}{l} Q\ \end{array}}$
=> Work done(W) = PD x Charge = 12 x 20 = 240J
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