Question

The current through a 60W lamp rated for 250V is
A) 0.24A
B) 4.2A
C) 0.5A
D) 6A

Answer 1

Hint: In this question, power and voltage is given we have to find out the value of current. For this we use the formula which relates the power, voltage and current i.e. $ P = VI $ , on substituting the values we can easily find the value of current.

Complete step by step solution
As, it is given that
Power of the lamp is $ P = 60W $
And the voltage across the lamp is $ V = 250V $
We have to find the value of current.
For this, we know that the power is equal to the product of voltage and current. Therefore, we can write it as $ P = VI $
P is power of the lamp and V is the voltage across the lamp and I is the current passing through the lamp.
We can write above formula as $ I = \dfrac{P}{V} $
Now, substitute the given values of P and V in above equation, we get
 $ \Rightarrow I = \dfrac{{60}}{{250}} $
 $ \Rightarrow I = 0.24A $
Hence, the current through a 60W lamp of rated 250V is 0.24A.
Therefore, option A is correct.

Note:
Electrical power is defined as the rate of consumption of energy or the rate of doing work i.e. $ power = \dfrac{{work}}{{time}} $
And we also know that the work done by current I when it flows in potential V at time t is $ W = VIt $
On substituting this value in the formula of power, we get
 $ \Rightarrow P = \dfrac{{VIt}}{t} = VI $
In this way we can derive the expression of power.