A 1 kW heater is meant to operate at 200 V.
a. what is the resistance ?
b. How much power will it consume if the line voltage drops to 100 V ?
c. How many units of electrical energy will it consume in a month ( of 30 days) if it operates 10 h daily at the specified voltage (200 V) ?

Question

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Answer 1

a. The resistance of electric appliance is given by
$R = \frac{V _{s}^{2}}{P _{0}} = \frac{( 2 0 0 ) ^{2}}{1 0 0 0} = 40 Ω$
b. The 'actual power' consumed by an electric appliance is given by
$P = (\frac{V _{A}}{V _{5}})^{2} \times P_{0} = (\frac{1 0 0}{2 0 0})^{2} \times 1000 = 250 W$
c. The total electrical energy consumed by an electric appliance in a specified time is given bt
$E = \frac{\sum w _{i} h _{i}}{1 0 0 0} k W h = \frac{1 0 0 0 \times ( 1 0 \times 3 0 )}{1 0 0 0} = 300 k W h$

Answer 2

a. The resistance of electric appliance is given by

R = \frac{V _{s}^{2}}{P _{0}} = \frac{( 2 0 0 ) ^{2}}{1 0 0 0} = 40 Ω

b. The 'actual power' consumed by an electric appliance is given by

P = (\frac{V _{A}}{V _{5}})^{2} \times P_{0} = (\frac{1 0 0}{2 0 0})^{2} \times 1000 = 250 W

c. The total electrical energy consumed by an electric appliance in a specified time is given bt

E = \frac{\sum w _{i} h _{i}}{1 0 0 0} k W h = \frac{1 0 0 0 \times ( 1 0 \times 3 0 )}{1 0 0 0} = 300 k W h