Question

An electric heater of resistance 1000 ohm works on 230V supply. Calculate the electrical energy consumed when heater works for 1 hour

Answer 1

Answer:

Power =P=VI⟹1000=250I⟹I=2501000=4A

∴(i) Electric current flowing through heater=I=4A

∴(ii) Resistance of heated wire R=IV=4250=62.5Ω

∴(iii) Thermal energy produced per minute by heater=ET=P×1min=1000×60sec=60000J

∴(iv) Electrical energy spent in kilowatt-hour by heater in 2 hours=1000PKW×2hour=2KW-hour

Answer 2

Concept:

The power of any electric device can be defined as

P = V²/R

where V is the operating voltage and R is the resistance.

Given:

The resistance of the electric heater is 1000 ohm and works on a 230 V supply.

Time, t = 1 hour = 3600 s

Find:

The electric energy which is consumed when the heater is working for 1 hour.

Solution:

Power consumed by the heater,

P = V²/R

P = (230)²/100

P = 529 W

Power consumed can be defined as the energy consumed per unit of time,

P = E/t

E = P×t

E = 529×3600 = 1904400 J

E = 1904.4 kJ

Hence, the electrical energy consumed when the heater works for 1 hour is 1904.4 kJ.

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