Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:

(i) the total current taken from the supply

(ii) the resistance of each heater and

(iii) the energy supplied in kWh to the three heaters in 5 hours.

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1 Answers

Given,

Power, p = 250 w

Voltage, v = 100 v

(i) current through each heater, I = ?

As p = VI

⇒ I = P/V

= 250/100 = 2.5 A

∴ Current taken for the three heaters = 3 × 2.5 = 7.5 A

(ii) resistance for each heater, R = V/I

= 100/2.5 = 40Ω

(iii) Time for which energy is supplied, t = 5h

As, Energy, E = p × t

E = 250 × 5 = 1250 wh

Or 

E = 1.25 kwh

Energy for three heaters = 3 × 1.25 = 3. 75 kwh

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