Energy

Question 1

What type of energy store does a battery have?

Answer 1

Chemical

Question 2

What type of energy store does a spring have?

Answer 2

Elastic Potential

Question 3

What type of energy store does a blowtorch has?

Answer 3

Thermal

Question 4

Energy cannot be…

Answer 4

created or destroyed

Question 5

A basketball player throws the ball into the hoop. Describe the change in energy store that has taken place as the ball

Answer 5

Kinetic to Gravitational

Question 6

Storage heaters contain bricks which warm up and store heat energy.
The bricks in this heater have a mass of 40 kg and are heated from 18 oC to 40 oC. If the specific heat capacity of the brick
material is 850 J/kg oC, calculate the change in thermal energy during heating.

Answer 6

Change in thermal energy = Mass x Specific Heat Capacity x Temperature Change
ΔE = m x c x Δθ

Temperature change Δθ = 40 – 18 = 22 oC
change in thermal energy ΔE = 40 x 850 x 22
ΔE = 748 000 J or 748 kJ

Question 7

In a “closed” system ….

Answer 7

energy can be transferred but there is no net energy loss.

Question 8

The energy transfer diagram for a mobile phone shows that 100 J of electrical energy produces 45 J of light energy and 36 J of sound energy.
How much thermal energy will be dissipated by the phone?

Answer 8

45 J + 36 J = 81 J
100 J – 81 J = 19 J
19 J of thermal energy will be dissipated

Question 9

Describe how the thermal energy produced by a bus driving along a road is dissipated.

Answer 9

The thermal energy increases the kinetic energy of the air particles therefore warming up the surroundings.

Question 10

. State why the total energy supplied to an electric fan must always equal the total energy transferred by the electric fan.

Answer 10

Energy can not be created or destroyed so:

total energy in = total energy out

Question 11

• The diagrams show two different types of loft insulation. Fiberglass insulation & Wool insulation
• The wool needs to be thicker to have the same insulating properties. Explain which material has the highest thermal conductivity?

Answer 11

Wool has the highest thermal conductivity as it lets thermal energy through at a faster rate so a thicker layer is needed for the same insulation as the fiberglass.

Question 12

Explain how trapped air reduces the rate of heat loss, in terms of thermal conductivity.

Answer 12

The air trapped inside the fiberglass acts as an insulator because air has a very low thermal conductivity and thermal energy can not pass through it easily.

Question 13

The motor for a lift in a tall building uses 12 000 W of power. The lift and its passengers has a mass of 500 kg. The lift motor takes 10 s to raise the lift and its passengers through a height of 20 m.
Work out the percentage efficiency of the lift motor.

Answer 13

• Efficiency = power out x 100 ÷ power in
• Power out = 5000 N x 20m
• Efficiency = 10 000 x 100 = 83 %

Question 14

The low energy bulb below uses 18 000 J of energy in one hour. If the efficiency of the low energy bulb is 78 %. Work out the amount of light energy given off by the bulb in one hours

Answer 14

• Efficiency = energy out x 100 ÷ energy in

- Energy out = 78 x 18 000 J = 14 040 J

Question 15

What is a fossil fuel?

Answer 15

A fuel formed in the geological past from the remains of living organisms.

Question 16

List all the renewable energy sources

Answer 16

Bio-Fuels, hydro-electricity, wind turbines, coal, solar power

Question 17

List all the non-renewable energy sources

Answer 17

Oil, nuclear, wind turbines, wave energy

Question 18

What is a renewable energy source?

Answer 18

An energy source that can be replenished as it is used.

Question 19

Why are fossil fuels considered to be a more reliable energy resource than renewable energy sources?

Answer 19

Produce a consistent energy supply with no gaps in energy delivery.

Question 20

Despite a large investment by the UK government in wind power, the amount of fossil fuel used has not seen a decline. Give a possible explanation for this.

Answer 20

UK is using more energy and wind power can not meet this rise in demand.

Question 21

The UK government is committed to investing in a “blend” of energy types to provide the UK’s energy needs for the next 100
years. Give an advantage of this rather than using just coal.

Answer 21

Evens out any variations in supply or cost of the energy source. Using only coal, if supplies stopped or the cost went up greatly, this would have a great impact on the consumer.

Question 22

A graph shows the world use of renewable energies over the past sixty years. Why has the use of wood increased very little over this time?

Answer 22

Limited supplies of wood and it takes a long time to grow new supplies. Also, pressure and legislation to prevent many trees from being cut down.

Question 23

A lot of money has been invested in wind turbines. Why does this energy source not produce as much as any other renewable resource?

Answer 23

Each wind turbine only produces a small amount of electricity and not enough have been installed to match production from other renewable resources.

Question 24

Describe how human activities have contributed to the greenhouse effect?

Answer 24

Burning fossil fuels for heating, transport and industry has led to a build up of carbon dioxide in the atmosphere (along with other greenhouse gases).