Question

For a heater rated at 4 kW and 220 V, calculate :

(a) the current,

(b) the resistance of the heater,

(c) the energy consumed in 2 hours, and

(d) the cost if 1 kWh is priced at Rs 4.60.

Answer 1

Given,

Power P = 4 kW,

Voltage, V= 220 V
(a) We know that, P = VI.

Therefore current I = P/V = 4 kW/220 V = 4000 W/220 V = 18.18 A.

(b) Resistance of the heater R = V/I = 220 V/18.18 A = 12.1 Ω.
(c) Energy consumed in 2 h = Pt = 4 kW x 2h = 8 kWh.
(d) If cost of 1 kWh = Rs. 4.60, then cost of 8 kWh of energy = Rs. 4.60 x 8 = Rs.36.80.