Question

An electric heater of resistance 8 ohm draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.​

Answer 1

Solution:-

Given:-

Resistance ( R ) = 8Ω

Current ( I ) = 15 A

Time ( t ) = 2 hrs

To find

Heat developed in heaters

Method = 1

Formula:-

P = I²R

Now , we get

P = (15)² 8

p = 15 × 15 x 8

p = 225 × 8

p = 1800 j / s

So

Heat is developrd in heater at rate 1800 j/s

Method =2

By using joules law

H = I²RT

now divide by T on both side

H/T = I²RT/T = I²R

=15 × 15 × 8

= 225 × 8

= 1800 J / S

Total amount of heat generated

=> E = pt

=> E = 1800 w × 2 h

=> E = 3 .6 kwh