Advertisements
Advertisements
Question
An electric heater of power 3 kW is used for 10 h. How much energy does it consume? Express your answer in
- kWh,
- joule.
Advertisements
Solution
Given:
Power of Heat P = 3 kW
Time t = 10 h.
(i) Energy consumed = power × time
Energy = 3 kW × 10 h = 30 kWh
(ii) 1 kilowatt hour (kWh) = 3.6 × 106 J
30 kWh = 30 × 3.6 × 106 J
= 108 × 106 J
= `108/100 xx 100 xx 10^6` J
= 1.08 × 108 J
APPEARS IN
RELATED QUESTIONS
A pump on the ground floor of a building can pump up water to fill a tank of volume 30 m3 in 15 min. If the tank is 40 m above the ground, and the efficiency of the pump is 30%, how much electric power is consumed by the pump?
Rajan exerts a force of 150 N in pulling a cart at a constant speed of 10 m/s-1. Calculate the power exerted.
1 H.P. = .........
Match the following
| column A | Column B |
| A stone at a height | power |
| A Moving ball | joule |
| Energy | work done in 1 s |
| Power | potential energy |
| Watt | kinetic energy |
A pump raises water by spending 4×105J of energy in 10s. Find the power of the pump.
Choose one or more correct alternatives.
Power is a measure of the ______.
- The rapidity with which work is done.
- Amount of energy required to perform the work.
- The slowness with which work is performed.
- Length of time.
A wind-powered generator converts wind energy into electric energy. Assume that the generator converts a fixed fraction of the wind energy intercepted by its blades into electrical energy. For wind speed v, the electrical power output will be proportional to ______
A bullet of mass 20 g strikes a pendulum of mass 5 kg. The centre of mass of the pendulum rises a vertical distance of 10 cm. If the bullet gets embedded into the pendulum, calculate its initial speed.
An engine pumps up 200 kg of water through a height of 20 m in 10 seconds. If the efficiency of the engine is 80%. Calculate the power of the engine.
