Energy Transformation

Q.

How does fan work?

Q.

In a loudspeaker, ___ energy is converted into sound energy.

1. electrical

2. Mechanical

3. Nuclear

4. Gravitational

Q. A ball of mass ‘m’ is dropped from a height ‘h’ above the ground. Calculate speed of the ball just before hitting the ground.

1. 2gh
2. gh
3. $\sqrt{2gh}$
4. $\sqrt{gh}$

Q.

In an electric bulb, electrical energy is converted into

1. Heat energy

2. Mechanical energy

3. Light energy

4. Both Heat and Light energy

Q.

A loudspeaker converts sound energy to electrical energy.

1. True

2. False

Q.

Give one example of heat energy to mechanical energy.

Q.

State the energy change that takes place when a ball is dropped from some height.

1. Kinetic energy to elevtrical energy

2. Mechanical energy to electrical energy

3. Potential energy to kinetic energy

4. Kinetic energy to potential energy

Q.

a toy car needs a sorce of energy to move.how could you give gravitational potential energy to a toy car so that it will move when you let it go

Q. State the energy changes that occur in a watch spring while it unwinds.

Q.

Which of the following is an example of conversion of mechanical energy to electrical energy ?

1. Working of motor

2. Working of Dynamo

3. Working of electric iron

4. Working of loud speaker.

Q.

I am a device that converts electrical signals to sound

Q. How does the telephone transform sound energy to electrical current?

Q.

In a bulb, electrical energy is converted into:

1. Heat energy

2. Mechanical energy

3. Light energy

4. Sound energy

Q.

In a photoelectric cell, the light energy gets converted into ___ energy.

Q.

What is the function of a photoelectric cell?

Q.

A stone weighing $1kg$is dropped from rest from a height of $4m$ above the ground. When it has free-fallen $1m$, what will be its total energy with respect to the ground?

Q. An object of mass 20 kg starts from rest and reaches a velocity of 10 m/s in 10 seconds. Calculate the power expended by the object.

1. 100 W
2. 100 w
3. 200 W
4. 300 W

Q.

When a person speaks in front of a microphone, the sound energy changes into :

1. Chemical energy

2. Electric energy

3. Loud sound energy

4. Magnetic energy

Q. Find the energy conversion in combustion of petrol.

1. Thermal - Chemical
2. Chemical - Mechanical
3. Chemical - Thermal
4. Thermal - Mechanical

Q.

When a stone is thrown in a lake of still water, ___ moves along the surface.

1. wave

2. stone

3. matter

4. water

Q.

A $60kg$ man moved $25$ steps up in $25s$. Find the power if each step is $16cm$ high. Take the value of $g=10m{s}^{-2}$.

Q. A boy of weight 500 N climb up a rope through a height of 10 m in 20 seconds. Calculate the power expended by him.

1. 100 W
2. 200 W
3. 250 W
4. 300 W

Q. In case of a fan, the energy conversion is from ___.

1. mechanical to electrical
2. electrical to mechanical
3. heat to light
4. chemical to electrical

Q.

What is visualization of sound ??

Q.

The ability to do work is called power.

1. True
2. False

Q. State the energy changes in the following while in use:
(a) An electric bulb
(b) An electric oven
(c) A loud speaker
(d) A microphone
(e) An electric motor

Q.

State the energy changes that occur in a watch spring while it unwinds.

Q. A body of mass $4kg$ is thrown upward from a height of $2m$ with an initial speed of $12m{s}^{-1}$. Its speed at height $3m$ is .

1. $10.1m{s}^{-1}$
2. $11.1m{s}^{-1}$
3. $12.1m{s}^{-1}$

Q.

Name the CGS Unit of work. How is it related to SI Unit of Work?

Q.

Water at the bottom of a waterfall becomes warmer than at the top. Explain, why?