Topic 1 - Energy

Question 1

What is specific heat capacity?

Answer 1

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

Question 2

Different materials and specific heat capacity

Answer 2

• Diff. Materials have diff specific heat capacities
• More energy needs to be transferred to the thermal energy store of some materials to increase their temperature than others

Question 3

What is SHC a measure of?

Answer 3

The measure of how much energy a substance can store

Question 4

What is efficiency?

Answer 4

• Some of the input energy is usually wasted by being transferred to a useless energy store - usually a thermal energy store
• The less energy wasted in this energy store, the more efficient the device is

Question 5

How to improve the efficiency of energy transfers:

Answer 5

• Insulating objects
• Lubricating objects
• Making objects more streamlined

Question 6

How to calculate the efficiency of energy transfers

Answer 6

Efficiency = Useful output energy transfer / total input energy transfer

Question 7

How to calculate the efficiency of power transfers:

Answer 7

Efficiency = useful output power / total input power

Question 8

Useful energy input and total energy output

Answer 8

Not always equal

Question 9

Devices and efficiency.

Answer 9

• NO device is 100% efficient

- Wasted energy usually transferred to useless thermal energy stores

Question 10

Electric heaters and efficiency

Answer 10

• An exception
• They’re usually 100% efficient because all the energy in the electrostatic energy store is transferred to ‘useful’ thermal energy stores

Question 11

Electric drills and efficiency

Answer 11

• It’s energy is transferred to lots of diff energy stores, but quickly ends up in all thermal energy stores
• Ultimately, all energy ends up transferred to thermal energy stores

Question 12

8 energy stores

Answer 12

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

Question 13

System

Answer 13

A single object (e.g. the air in a piston) or a group of objects (two colliding vehicles)

Question 14

Closed system definition

Answer 14

Systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero

Question 15

4 main ways energy is transferred

Answer 15

• Mechanically (by a force doing work)
• Electrically (work done by a moving charges)
• By heating
• by radiation (e.g. light or sound)

Question 16

Wind power

Answer 16

• Lots of little turbines in exposed places

- Each turbine has a generator inside, rotating blade turn the generator and produce electricity

Question 17

Advantages of wind turbines

Answer 17

• No pollution - apart for a bit when they’re manufactured
• No fuel costs and minimal running costs
• No permanent damage to landscape - can be removed

Question 18

Disadvantages of wind turbines

Answer 18

• They spoil the view
• Can be v noisy, annoying for people living nearby
• Turbines can stop when wind stops, what if winds also too strong?
• Impossible to increase supply when there’s extra demand
• Initial costs quite high

Question 19

Solar power

Answer 19

• Solar cells generate electric currents directly from sunlight
• Usually used to generate electricity on a relatively small scale

Question 20

Advantages of solar power

Answer 20

• No pollution (although factories use quite a lot of energy and produce some pollution when manufacturing the cells)
• In sunny countries its a v reliable source of energy in daytime
• Can still be cost effective in cloudy country’s like Britain
• Energy is free and running costs almost nil

Question 21

Disadvantages of solar power

Answer 21

• You can’t increase the power output when there’s extra demand
• Initial costs are high

Question 22

Where is solar power usually used

Answer 22

• Often best sources of energy to charge batteries in calculators and watches (don’t use much electricity)
• Powers electric road signs and satellites
• Used in remote places where there’s not much choice (e.g. the Australian Outback)

Question 23

Geothermal power

Answer 23

Uses energy from underground thermal energy stores to generate electricity or to heat buildings directly

Question 24

Advantages of geothermal power

Answer 24

• Brilliant free energy that’s reliable w/ v few environmental problems

Question 25

Disadvantages of geothermal power

Answer 25

• Only possible in volcanic areas where hot rocks lie quite near to the surface
• Cost of building a power plant is often high compared to the amount of energy it produces

Question 26

Hydroelectric power

Answer 26

Transfers energy from the kinetic energy of falling water m