An electric iron of resistance 20 Ω takes a current of 5 A
We have to calculate the heat developed in 30 s.
The amount of heat (H) produced is given by the joule’s law of heating as
Current (I) = 5 A
Time (t) = 30 s
Voltage (V) = Current x Resistance
V = 5 x 20
V = 100V
H= 100 x 5 x 30
H = 1.5 x 104 J.
Therefore, the amount of heat developed in the electric iron is 1.5 x 104 J.