Tag: energy transformations and energy transfers

Questions Related to energy transformations and energy transfers

What are the various energy transformations that occur when you are riding bicycle?

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

  1. Muscular $\rightarrow$ Kinetic $\rightarrow$ Heat

  2. Potential $\rightarrow$ Kinetic $\rightarrow$ Heat

  3. Kinetic $\rightarrow$ Heat $\rightarrow$ Sound

  4. None

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Correct Option: A
Explanation:

While paddling a bicycle muscular energy converted to kinetic energy as the bicycle moves.Rotation of wheel create friction causing loss of kinetic energy in the form of heat.

If $1kg$ of a substance is fully converted into energy , then the energy produced is  

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

  1. $9 \times 10^{16}J$

  2. $9 \times 10^{24}J$

  3. $1J$

  4. $3 \times 10^{8}J$

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Correct Option: A

An anti-aircraft shell has been fired and it has a kinetic energy x. It explodes in the air. Then the sum of kinetic energies of all the particles is:

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

  1. x

  2. more than x

  3. less than x

  4. zero

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Correct Option: B
Explanation:

During explosion, the chemical energy gets converted into kinetic energy. So, after explosion sum of kinetic energies of all the particles is greater than the initial kinetic energy.

In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because

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

  1. its temperature increases

  2. larger amount of potential energy is converted into kinetic energy

  3. the electricity content of water increases with height

  4. more water molecules dissociate into ions

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Correct Option: B
Explanation:

Hydroelectric power plant uses the potential energy stored in water to generate electricity.
Therefore, if we increase the height of it's fall, energy stored will also increase and large amount of potential energy will be converted into kinetic energy, which means more electric energy will be generated.

Choose the incorrect statement regarding wind power.

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

  1. Energy  from moving wind is wind energy.

  2. The potential energy content of wind blowing at high altitudes is the source of wind power.

  3. Wind hitting at the blades of a windmill causes them to rotate. The rotation thus achieved can be utilized further.

  4. One possible method of utilising the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator.

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Correct Option: B
Explanation:

The energy that we harness from a windmill is the wind energy due to moving air.
Here, option B is wrong as the wind energy does not depend on the altitude when we harness energy from the windmill.

Water falls from a height 500 m. What is the rise in  temperature of water at bottom if whole energy remains in the water?

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

  1. $0.96^0C$

  2. $1.02^oC$

  3. $1.17^oC$

  4. $0.23^oC$

Show answer
Correct Option: C
Explanation:
Water is at height $(h) = 500 \,m$.
Potential energy $= mgh$
$= 1 \times 9.81 \times 500$
$= 4905 \,J/litre$

Specific heat of water $= 4180 \,J/kg \,k$.
So, $E = mc \Delta T$.
$4905 = 1 \times 4180 \times \Delta T$
$\Delta T = \dfrac{4905}{4180}$
$\Delta T = 1.16^o C$.

When we rub our hands, which of the following is true?

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

  1. Mechanical energy converted to heat energy.

  2. kinetic energy converted to heat energy.

  3. Heat energy converted to mechanical energy.

  4. Heat energy converted to kinetic energy.

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Correct Option: A

A body off mass $5kg$ falls from a height of $30metre$. If its all mechanical energy is changed into heat, then heat produced will be 

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

  1. $ \text{350 cal} $

  2. $ \text{150 cal} $

  3. $ \text{60 cal} $

  4. $ \text{6 cal} $

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Correct Option: A

a piece of lead falls from a height of $100m$ on a fixed non-conducting slab which brings it to rest. If the specific heat of lead is $30.6{\rm{ }}cal/kg{\,^ \circ }C,$, the increase in temperature of the slab immediately after collision is 

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

  1. ${6.72^ \circ }C$

  2. ${7.62^ \circ }C$

  3. ${5.62^ \circ }C$

  4. ${8.72^ \circ }C$

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Correct Option: D

A metal ring of mass  2.1 kg and of 10 cm radius is revolving about its axis, Making 100/$\pi $ revoluation/s in the liquid is equal to 

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

  1. 100 cal

  2. 1000 cal

  3. 2100 cal

  4. 10 cal

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Correct Option: A