Question

1 In which of the following cases more electrical is consumed per hour? (a) A current of 1 Amphere passed through a resistance of 300 ohms. (b) A current of 2 Ampere passed through a resistance of 100ohms.

2 Electric kettle rated at 220V, 2.2kW works
for 3 hours. Find the energy consumed and the current drawn.​

Answer 1

Answer:

1.

If current is represented as 'i' resistance as 'r', and time 't', then electrical energy e is defined

as,

e = {i}^{2}*r*t

(Note: time in seconds = t*60 )

first case:

1*1*300*1*60

=18000 Joule

second case:

2*2*100*1*60

= 24000 Joule

Thus second case consumed more in a hour.

2.

Power, P = 2.2 kW = 2200 W

Voltage, V = 220 V

Time, t = 3 h = 3 × 3600 = 10800 s

So, the energy consumed is = 2200 × 10800 = 23760000 J

The current drawn is, I = P/V = 2200/220 = 10 A