SP3- Conservation of energy

Question 1

What are the main 8 energy stores?

Answer 1

Magnetic, 
Thermal (internal) 
Chemical
Kinetic
Electrostatic
Elastic potential 
Gravitational potential 
Nuclear

Question 2

What is a magnetic energy store and name some examples of this.

Answer 2

The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart. Fridge magnets, compasses etc.

Question 3

What is an internal (thermal) energy store and name some examples.

Answer 3

The total kinetic and potential energy of the particles in an object, in most cases this is the vibrations - also known as kinetic energy- of particles. In hotter objects, the particles have more internal energy and vibrate faster. Human bodies, stoves and hobs etc.

Question 4

What is a chemical energy store and name some examples.

Answer 4

The energy stored in chemical bonds, such as those between molecules. Foods, muscles, electrical cells.

Question 5

What is a kinetic energy store and name some examples.

Answer 5

The energy of a moving object. Runners, buses, comets.

Question 6

What is an electrostatic energy store and name some examples.

Answer 6

The energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart.

Question 7

What is an elastic potential energy store and name some examples.

Answer 7

The energy stored when an object is stretched or squashed. Drawn catapults, compressed springs, inflated balloons.

Question 8

What is a gravitational potential energy store and name some examples.

Answer 8

The energy of an object at height. Aeroplanes, kites, mugs on a table.

Question 9

What is a nuclear energy store and name some examples.

Answer 9

The energy stored in the nucleus of an atom. Uranium nuclear power, nuclear reactors.

Question 10

What are the 4 main processes that energy is transferred by? Describe how each one does this

Answer 10

Mechanical- a force moving on an object through a distance.
Electrical- charges moving due to a potential difference.
Heating- due to temperature difference caused electrically or by chemical reaction
Radiation- energy transferred as a wave, eg light and infrared

Question 11

How is energy transferred when a car brakes in an emergency?

Answer 11

Kinetic energy is transferred into thermal energy of the surroundings by the work done by the force of friction on the brakes.

Question 12

How is energy transferred when a snowball hits a wall?

Answer 12

Kinetic energy is transferred into thermal energy of the surroundings by the work done by the force from the wall.

Question 13

Energy can be transferred…

Answer 13

Usefully, stored or dissipated, but it cannot be created or destroyed.

Question 14

What happens to the conservation of energy when a skydiver jumps out of a plane?

Answer 14

He begins to lose energy from the gravitational potential energy store as his height decreases, and his kinetic energy store increases as his speed increases. However not all energy is transferred into the kinetic energy store. As some work is done pushing against the air particles, some of the GPE is transferred to the air particles and is stored as internal energy.

Question 15

What is the equation for change in gravitational potential energy?

Answer 15

GPE = mass x gravitational field strength x height

Question 16

What is the equation for kinetic energy?

Answer 16

KE = 0.5 x m x (v) squared

Question 17

What is a rise in temperature caused by?

Answer 17

The transfer of wasteful energy in mechanical processes. The energy is dissipated into the system.

Question 18

How is energy dissipated in a mechanical system?

Answer 18

When 2 surfaces rub together. Work is done against friction which causes heating of the two surfaces- so the internal (thermal) energy store of the surfaces increases and this is then transferred to the internal energy store of the surroundings.

Question 19

What can be used to reduce energy that is dissipated to the surroundings?

Answer 19

Lubrication can be used to prevent objects from rubbing together, therefore reducing the amount of thermal energy produced.

Question 20

How do you calculate efficiency?

Answer 20

Useful energy/total energy.

Question 21

Why can’t a device ever be 100% efficient?

Answer 21

Because this would mean that more energy is being transferred than is being supplied, which would mean that energy is being created. That would break the law of conservation of energy.

Question 22

How can insulation be used to improve efficiency?

Answer 22

By reducing the wasteful dissipation of thermal energy.

Question 23

To reduce thermal energy transferred from a warm house,…

Answer 23

The walls are built thicker, so the energy must travel further before it is transferred to the to the outside.

Question 24

How can thermal energy be reduced?

Answer 24

By using a cavity wall- two walls with an air gap between them so the air has a lower thermal conductivity than brick.

Question 25

What are systems that store large amounts of energy called?

Answer 25

Energy resources.

Question 26

What are the main energy resources available to produce electricity?

Answer 26

Fossil fuels, nuclear fuels, bio-fuel, wind, hydro-electricity, geothermal, tidal, water waves and the sun.

Question 27

What is a renewable energy source?

Answer 27

Energy sources that can be replenished/ created and will never run out.

Question 28

What is a non-renewable energy source?

Answer 28

Energy sources that will run out and cannot be created.