Topic 1 - Energy

Question 1

What is a system?

Answer 1

A system is an object or a group of objects

Question 2

Describe the energy changes when water is brought to boil in an electric kettle.

Answer 2

Electricity through the kettle increases the internal energy of the element which in turn increases the thermal energy of the water which increases the temperature of the water

Question 3

Describe the energy transfers that take place when an object is thrown into the air.

Answer 3

The object slows down as it goes up:

• energy is being transferred from the object’s kinetic energy store to it’s gravitational potential energy store.

Question 4

Describe the energy transfers that take place when an object falls freely.

Answer 4

The object speeds up as it falls:

• the force of gravity acting on the object causes energy to be transferred from it’s gravitational potential energy store.

Question 5

Describe the energy transfers that take place when a falling object hits the floor.

Answer 5

All of the energy in it’s kinetic energy store (transferred from the GPE store) is transferred to the thermal energy store of the object and the floor, and by sound waves moving away from the point of impact.

Question 6

Describe the energy transfers that take place when an object is subject to friction

Answer 6

Work done to overcome friction is mainly transferred to the thermal energy stores by heating:

• such as rubbing your hands

Question 7

What is useful energy?

Answer 7

Energy transferred to where it is wanted in the way it is wanted.

Question 8

What is wasted energy?

Answer 8

Energy that is not usefully transferred.

Question 9

What is specific heat capacity?

Answer 9

The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1°C

Question 10

What is power?

Answer 10

The rate at which energy is transferred or the rate at which work is done

Question 11

What is the principle of conservation of energy?

Answer 11

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

Question 12

Describe 2 ways of reducing unwanted energy transfers (wasted energy).

Answer 12

• Lubrication decreases the friction of an object, meaning less energy is transferred as thermal energy to the surroundings (wasted as it is not useful).
• Using insulation(reducing the energy loss by using a material with low thermal conductivity)

Question 13

What are the uses of energy resources?

Answer 13

• transport
• electricity generation
• heating.

Question 14

What is The National Grid?

Answer 14

A system of cables and transformers linking power stations to consumers.

Question 15

What 4 ways can energy be transferred?

Answer 15

• mechanical work
• electrical work
• heating
• radiation

Question 16

What is mechanical work?

Answer 16

a force moving an object through a distance

Question 17

What is electrical work?

Answer 17

charges moving due to a potential difference

Question 18

What is heating transfer?

Answer 18

due to temperature difference caused electrically or by chemical reaction

Question 19

What is radiation transfer?

Answer 19

energy transferred as a wave, eg light and infrared - light radiation

Question 20

What is potential difference?

Answer 20

Voltage - measure of how much energy is transferred between two points in a circuit.

Question 21

What is Power?

Answer 21

Power is defined as the rate at which energy is transferred or the rate at which work is done

Question 22

What is the rule regarding thermal conductivity and energy transfer?

Answer 22

The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

Question 23

What dictates the rate of cooling of a building?

Answer 23

The rate of cooling of a building is affected by the thickness and thermal conductivity of its walls

Question 24

What is thermal conductivity?

Answer 24

Thermal conductivity is a measure of how well a material conducts energy when it is heated.

Question 25

What is internal energy?

Answer 25

the total amount of kinetic energy and potential energy of all the particles in the system

Question 26

What is potential energy?

Answer 26

This type of energy that is stored in a body and has the potential to do work.