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प्रश्न
Name the material commonly used for the manufacturing of solar cells.
उत्तर
Silicon and Gallium. Solar cell produces d.c. current. State whether a solar cell produces a.c. or d.c. current.
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संबंधित प्रश्न
Give reasons for the following. No work is done if a man is pushing against a wall.
Give reasons for the following A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work.
When is work said to be done by a force?
.A man raises a box of mass 50kg to a height of 2m in 20s, while another man raises the same box to the same height in 50s. Compare:
(i) the work done, and
(ii) the power developed by them.
In which of the following case the work done by a force will be maximum : when the angle between the direction of force and direction of motion is 0° or 90°?
A max X goes to the top of a building by a vertical spiral staircase. Another man Y of the same mass goes to the top of the same building by a slanting ladder. Which of the two does more work against gravity and why?
A boy tries to push a truck parked on the roadside. The truck does not move at all. Another boy pushes a bicycle. The bicycle moves through a certain distance. In which case was the work done more : on the trick or on the bicycle? Give a reason to support your answer.
Give two examples of work done.
Complete the following sentences:
The SI unit of work is ....... and of power is .......
A body does 20 J of work in 10 s. What is its power?
Give an example
Chemical energy changes to electrical energy.
How long should an electric motor, of power 2 H.P. operate, so as to pump 5 m3 of water from a depth of 15m. [Take g = 10 N kg−1]
A bucketful of water is to be drawn from a well ______ will be done when a ______ is applied to do this because there will be a ______ of water.
(displacement, work, force)
If a ball is dropped on the sloping roof of a house, it acquires ______ and falls on the ground. That is the transformation of ______ energy into ______ energy takes place.
(kinetic, potential, motion)
Write the two main conditions are needed for work to be done?
State whether work is done or not, by writing yes or no, in the following case:
A boy climbs up 20 stairs.
