Tag: energy transformations and energy transfers

Questions Related to energy transformations and energy transfers

Which of the following statements is correct?

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. Kinetic energy of a system can be changed without changing the momentum

  2. Kinetic energy of a system cannot be changed without changing its momentum

  3. Momentum of a system cannot be changed without changing its kinetic energy

  4. A system cannot have energy without having momentum

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Correct Option: A
Explanation:

Answer is A

Momentum is a vector quantity while K.E is a scalar quantity ,we can change velocity in such a way momentum remains same but K.E changes .

A solar water heater converts

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. Light energy into heat energy

  2. Heat energy into light energy

  3. Chemical energy into heat energy

  4. Light energy into electrical energy

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Correct Option: A
Explanation:

Solar heater absorbs light, and thus photons of light are absorbed and the energy contained in them is converted to heat energy, which raises the temperature of water flowing slowly in contact with the plate and thus heat energy is transfered from plate to water.

Hence a solar heater converts light energy into heat energy.
Option A.

The temperature of water at the bottom of a waterfall is higher than that of the water at the top, because:

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. falling water absorbs heat from the sun.

  2. kinetic energy of the falling water is converted into heat.

  3. water at the bottom has greater potential energy.

  4. the rocks on the river bed give out heat.

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Correct Option: B
Explanation:

When water is flowing it posses some kinetic energy and also posses some potential energy wrt to the lower level of the waterfall.

When water fall from higher level its potential energy gets converted to kinetic energy and when water reaches to lower level some part of its kinetic energy gets converted to sound energy amd some to heat energy.
So best possible option is option B.

Burning of a meteorite in the earth's atmosphere is an example of change of :

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. heat energy into kinetic energy

  2. kinetic energy into heat energy

  3. kinetic energy into potential energy

  4. potential energy into heat energy

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Correct Option: B
Explanation:

A meteorite has both potential and kinetic energy before entering earth's atmosphere. As it enters and fall towards the surface of earth, frictional heating occurs which is caused by collision with the molecules in the atmosphere which reduces its velocity. Hence the kinetic energy decreases, which is converted into heat energy. Potential energy is continuously decreasing being converted to kinetic energy.

When fuels are burnt, chemical energy changes into:

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. kinetic and potential energy

  2. solar energy

  3. heat and light energy

  4. nuclear energy

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Correct Option: C
Explanation:

Fuels contain chemical energy stored in them. When fuels are burnt, the chemical energy changes into heat and light energy.

A ball is placed on a compressed spring. On releasing the spring, the ball flies away. Then which of the following is true?

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. The ball creates its own kinetic energy

  2. Elastic potential energy of the spring is destroyed and kinetic energy of the ball is created

  3. Potential energy of the ball is destroyed and kinetic energy of the spring is created

  4. Elastic potential energy of the spring gets converted into kinetic energy of the ball

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Correct Option: D
Explanation:

Work is done on the spring to compress it. This work is stored in the spring in the form of its elastic potential energy. When the spring is released, its elastic potential energy gets transformed into the kinetic energy of the ball and the ball flies away.

Which of the following devices converts electrical energy into heat energy?

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. A dynamo

  2. An electric iron

  3. A loud speaker

  4. A thermocouple

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Correct Option: B
Explanation:

An electric iron converts electrical energy into heat energy.

Buming of a meteorite in the Earth's atmosphere is an example of change of:

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. heat energy into kinetic energy

  2. kinetic energy into heat energy

  3. kinetic energy into potential energy

  4. potential energy into heat energy

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Correct Option: B
Explanation:

when meteorite falls its potential energy is converting into kinetic energy and when it enters earth atmosphere due to air friction its kinetic energy is reduced but potential energy is also decreasing as its height is decreasing , so we can conclude that its first potential energy converts to kinetic energy and then kinetic energy converts to heat energy.

so best possible answer is option B.

A generator is an arrangement which converts _________ energy into _________ energy.

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. mechanical, electrical

  2. mechanical, chemical

  3. potential, electrical

  4. electrical, chemical

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Correct Option: A
Explanation:

 A generator converts mechanical energy into electrical energy.  Generator works due to this because of electromagnetic induction generated due to this conversion of energy. Also magnetic field is produced which results in generation of voltage that helps the generator to function.

A motor converts:

physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

  1. electrical energy into mechanical energy

  2. mechanical energy into electrical energy

  3. electrical energy into heat energy

  4. heat energy into electrical energy

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Correct Option: A
Explanation:

A motor converts electrical energy into mechanical energy.