Advertisements
Advertisements
Question
Find the energy in joules consumed in 10 hours by four devices of power 500 W each.
Solution
The power of four devices = 4 × 500 W
= 2000 W
Time = 10 hours
Therefore,
The energy consumed = power × time
= 2000 × 10 Wh
= 20000 Wh
= 20 kWh
= 20 units. ...[1 unit = 1 kWh]
APPEARS IN
RELATED QUESTIONS
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
Define average power.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
Name the physical quantity whose unit is watt.
What is the power of a body which is doing work at the rate of one joule per second?
A trolley is pushed along a road with a force of 400 N through a distance of 60 m in 1 minute. Calculate the power developed.
A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s. Calculate : work done by the car.
A boy weighing 40 kg carries a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 m/s2)
In an experiment to measure his power, a student records the time taken by him in running up a flight of steps on a staircase. Use the following data to calculate the power of the student :
Number of steps = 28
Height of each step = 20 cm
Time taken = 5.4 s
Mass of student = 55 kg
Acceleration = 9.8 m s−2
due to gravity
In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
How much work does he do in lifting one box?
