A 1kW heater is meant to operate at 200 V. (a) What is its 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 hr daily at the specified voltage?

Explanation

a) The resistance of an electric appliance is given by,
`R=(V_(S)^(2))/(W)" so, "R=((200)^(2))/(1000)=40Omega`
b) The .actual power. consumed by an electric appliance is given by,
`P=((V_(A))/(V_(S)))^(2)xxW" so, "P=((100)/(200))^(2)xx1000=250W`
c) The total electrical energy consumed by an electric appliance in a specified time is given by,
`E=(SigmaW_(1)h_(1))/(1000)kWh`
`"So, "E=(1000xx(10xx30))/(1000)=300kWh`