Energy

Question 1

Write down four energy stores

Answer 1

• Thermal energy stores
• Kinetic energy stores
• Gravitational potentail energy stores
• Elastic potential energy stores
• Chemical energy stores
• Magnetic energy stores
• Electrostatic energy stores
• Nuclear energy stores

Question 2

Describe how energy is transferred as a ball falls to the ground

Answer 2

A ball dropped from a height is accelerated by gravity. the gravitational force does work. It causes energy to be transferred from the ball’s gravitational potential energy store to its kinetic energy store

Question 3

Give the equation for calculating the amount of energy in an object’s kinetic energy store

Answer 3

Kinetic energy (J)= 1/2 x mass(kg) x Speed^2 (m/s)^2

Question 4

If energy is transferred to an object’s kinetic energy store what happens to its speed

Answer 4

It speeds up

Question 5

Give the equation for finding the energy in an object’s gravitational potential energy store.

Answer 5

G.P.E(J)= Mass(kg) x Gravitational field strength (N/kg) x height(m)

Question 6

What kind of energy store is energy transferred to when you compress a spring

Answer 6

Elastic potential energy store

Question 7

What is the definition of the specific heat capacity of a material

Answer 7

Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1*C

Question 8

Give the equation that relates energy transferred and specific heat capacity

Answer 8

Change in thermal energy(J)= Mass(kg) x Specific heat capacity (J/kgC) x Temperature change (C)

Question 9

Describe an experiment to find the specific heat capacity

Answer 9

Heat up a block of material wrapped in insulation using a power supply. As the block heats up take readings of temperature and current every minute for 10 minutes. Calculate power supplied to the heater which you can use to calculate how much energy has been transferred to the heater. Assuming all energy supplied to the heater is transferred to block plot a graph of energy transferred to thermal energy store against temperature. Find the gradient of the line so the specific heat capacity of the material of the block is 1/(Gradient x mass of block)

Question 10

State the conservation of energy principle

Answer 10

Energy can be transferred usefully, stored or dissipated but can never be created or destroyed

Question 11

Define power and give two equations to calculate power.

Answer 11

Power is the rate of energy transfer or rate of doing work.

Power(W)=Energy transferred(J)/Time(s) or Power(W)=Work done(J)/Time(s)

Question 12

What are the units of power

Answer 12

Watts, one watt= 1joule of energy transferred per second

Question 13

Does a high thermal conductivity mean there is a high rate of energy transfer

Answer 13

Yes, materials with a high thermal conductivity transfer energy between their particles quickly

Question 14

How can you reduce unwanted energy transfers in a machine with moving, touching components

Answer 14

Lubricants can be used to reduce the friction between objects’ surfaces when they move. Lubricants are usually liquids like oil so that they can flow easily between objects and coat them.

Question 15

Give four ways to prevent unwanted energy transfers in a home

Answer 15

• Cavity walls. Walls with air gaps in the middle reducing conduction
• Loft insulation. Reduces convection currents being created in lofts
• Double glazed windows. Air gap between sheets o f glass to less heat is lost by conduction
• Draught excluders around doors and windows reduce energy transfers by convection

Question 16

Do thicker walls make a house cool down quicker

Answer 16

Thicker walls will have a slower rate of energy transfer therefore heat is lost slower

Question 17

Describe an experiment you could do to investigate how good a material is as a thermal insulator

Answer 17

Measure the temperature difference in a sealable container with and without insulation. The lower the temperature difference the better the material acts as an insulator

Question 18

What is the efficiency of an energy transfer? Give the equation that relates efficiency to power

Answer 18

How much energy is wasted by being transferred to a useless energy source. The less energy wasted the more efficient it is.
Efficiency=Useful output energy transfer or power output/Total input energy transfer or power output

Question 19

Name four renewable energy sources and four non renewable energy resources

Answer 19

Renewable: Solar, wind, water waves, hydroelectricity, biofuel, tides and geothermal
Non-renewable:Coal, oil, (natural) gas and nuclear fuel

Question 20

What is the difference between renewable and non renewable energy resources

Answer 20

Non renewable energy resources will run out one day while renewable energy resources will not. Renewable energy resources usually do less damage than non renewable however these are more reliable.

Question 21

Give an example of how a renewable energy resource is used in everyday life

Answer 21

Geothermal heat pump uses geothermal energy resources to heat buildings. Solar water heaters use the sun to heat water which is pumped into radiators. Burning bio-fuel or using electricity generated by renewable resources can also be used for heating.

Question 22

Explain why solar power is considered to be a fairly reliable energy resource.

Answer 22

In sunny countries solar power is a very reliable source as there is usually a lot of sunlight. However this is only during daytime

Question 23

Describe one way of reducing the environmental impact of using fossil fuels

Answer 23

Acid rain can be reduced by taking the sulfur out before the fuel is burned, or cleaning up the emissions

Question 24

Give one environmental benefit of using nuclear power

Answer 24

Nuclear power is clean

Question 25

Explain why the UK plans to use more renewable energy resources in the future

Answer 25

To protect the environment as well as learning to go without non renewables since these will run out eventually.