Question

An electric kettle is rated 500W , 220 V . It is used to heat water for 30 seconds. Assuming the voltage to be 220 V, calculate the heat produced.

Answer 1

Answer:

15000J is the heat produced.

Explanation:

The energy consumed and power are related as :

$u\;=\;P\times\;t$

• $500W\times30s$

• $15000J$

∴ Heat produced is 15000J.

Answer 2

P = 500 W  

V = 200 Volt

Source voltage = 220 V

m = 400 g = 0.4 kg

t = 30 s

s = 4200 Jkg-1/0C

First we find the resistance of the heater

We have

P = V2/R

=> R = V2/P

=> R = 2002/500  

 = 80ΩΩ  

Now power given out by the heater at 220V supply will be

P = 2202/80

 = 605 W

Heat given out  

Q = P×t

 = 605×30 =  18150 J