An electric heater of resistance $8 \Omega$ draws $15 \mathrm{~A}$ from the service mains for 2 hours.

Question.
An electric heater of resistance $8 \Omega$ draws 15 A from the service mains for 2 hours. Calculate the rate at which heat is developed in the heater.

solution:

Here, $\mathrm{I}=15 \mathrm{~A}, \mathrm{R}=8 \Omega, \mathrm{t}=2 \mathrm{~h}$

Rate at which heat is developed, i.e, electric power, $\mathrm{P}=\mathrm{I}^{2} \mathrm{R}=(15)^{2} \times 8=1800 \mathrm{~W}$

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