P1 Topic 5 - Generation And Transmission Of Electricity

Question 0

What is voltage?

Answer 0

Voltage - is the electrical pressure giving a measure of the energy transferred.

Question 1

What is current?

Answer 1

Current - the rate of flow of charge around a circuit. Electrons usually carry the charge - they are negatively charged particles.

Question 2

What are A.C. and D.C.?

Answer 2

A.C. or alternating current keeps changing direction, the mains electricity is a.c.

D.C. or direct current always flows in the same direction, batteries and solar cells

Question 3

What is electrical power?

Answer 3

Electrical Power - the energy transferred per second, units are Watts

Question 4

How do you calculate power?

Answer 4

Power (W) = Voltage (V) x Current (I)

Question 5

How do you measure the current and voltage of a circuit?

Answer 5

Current:
Use an ammeter
Place it in series (part of the circuit)

Voltage:
Use a voltmeter
Connect in parallel

Question 6

How do you generate electricity using a coil of wire and a magnet?

Answer 6

You can induce a voltage in a conductor by moving a magnet in or near the coil of wire. This is called electromagnetic induction.

As you move the magnet, the magnetic field through the coil changes, this change in magnetic field induces voltage and causes a current to flow in the wire so long as it part of a complete circuit.

Question 7

What four factors affect the size of the voltage induced by a magnet and coil of wire?

Answer 7

1) The strength of the magnet
2) The area of the coil
3) The number of turns on the coil
4) The speed of the movement

Question 8

Name the four non-renewable energy resources.

Answer 8

Coal
Oil
Gas
Nuclear

Question 9

What are the environmental problems of using non-renewable energy sources?

Answer 9

• All three fossil fuels release CO2 and CO.
  > Contributes to global warming and greenhouse effect
• Burning coal and oil releases sulphur dioxide
  > Causes acid rain
• Coal mining ruins the landscape, especially with open-cast mining
• Oil spillages cause serious cause serious environmental problems
• Nuclear power creates nuclear waste which is very dangerous and can be difficult to dispose of
• Nuclear power carries the risk of major catastrophes, such as Chernobyl

Question 10

How do power stations make energy?

Answer 10

The coal, oil or gas is burnt (chemical energy into heat energy) and the heat is used to boil water into steams the steam turns a turbine (heat energy into kinetic energy) connected to a generator. As the generator turns, it induces a voltage (kinetic energy into electrical energy) using electromagnetic induction.

Question 11

How do nuclear power stations make energy?

Answer 11

Nuclear fission is used to boil water (nuclear into heat).
The steam is used to turn a turbine (heat into kinetic).
The turbine is connected to a generator that induces a voltage with electromagnetic induction (kinetic into electrical).

Question 12

What are the 7 renewable energy sources?

Answer 12

Hydroelectricity
Wave power
Tidal Barrages
Wind power
Solar cells
Geothermal energy
Burning natural waste

Question 13

How does hydroelectricity produce electricity?

Answer 13

• A valley is usually flooded and then blocked with a big dam.
• Rain water is caught in the dam and allowed through turbines.
• The turbines are connected to generators which produce energy.

Question 14

How does wave power produce electricity?

Answer 14

• Waves provide an up and down motion which forces air in and out of a turbine.
• The turbine is connected to a generator which makes power.

Question 15

How do tidal barrages produce electricity?

Answer 15

• Big dams with turbines in them are built across estuaries.
• As the tides comes in, the height of the water in the estuary increases and the water can be let out slowly through the turbines.

Question 16

How does wind power produce electricity?

Answer 16

• Each wind turbine has its own generator so electricity is produced directly when wind turns the blades.

Question 17

How do solar cells produce electricity?

Answer 17

• As the sun shines on the cells, they generate a current from the light energy.

Question 18

How does geothermal energy produce electricity?

Answer 18

• Cold water is pumped down to hot rocks near the surface (~7km).
• The water heats up and turns into steam and is pumped back to the surface.
• The steam turns a turbine which is connected to a generator.

Question 19

How does biomass produce electricity?

Answer 19

• Biomass can be anything from farm waste, animal droppings, landfill rubbish or specially grown forests.
• The biomass is burnt and makes energy similarly to fossil fuels.

Question 20

What are the advantages and disadvantages of the following renewable energy sources:
Hydroelectricity
Wave Power
Tidal Barrages
Wind Power
Solar Cells
Geothermal Energy
Biomass

Answer 20

Hydroelectricity:
X Big impact on the environment as large areas have to be flooded which destroys the habitat of many species
X Initial costs are high
O Immediate response to increased electricity demand, more water can be let out through the turbines
O Minimal running costs
O Reliable source of energy

Wave Power:
X Fairly unreliable, waves stop when wind dies out
X Doesn’t produce much energy
O Useful for producing energy from small islands
O Offshore wave farms can be built further out in the ocean where the waves are more powerful

Tidal Barrages
X Can only be used on some estuaries that are suitable enough
O Reliable energy source

Wind Power
X Wind turbines spoil the view
X Only work when there is wind, so may not be able to supply electricity when demand is higher
O No pollution

Solar Cells
X Only produces energy during the daytime
X Usually used to generate energy on a small scale
O Reliable source of energy

Geothermal Energy
X Only possible where there are hot rocks near the surface
O High setup costs
O No environmental problems

Biomass
O The plants that grew to produce the waste took in CO2 from the atmosphere. When the waste is burnt, the same CO2 is released so there is no extra contribution. This means that burning biomass is carbon neutral.

Question 21

What 6 factors have to be taken into consideration when building a power station?

Answer 21

Set-up costs
Reliability issues
Set-up time
Running/fuel costs
Environmental issues
Location issues

Question 22

What do transformers do and how do they work?

Answer 22

There are two types of transformers: step-up and step-down

Their purpose in the National Grid is to increase the voltage and minimise the loss of current and then decrease the voltage to safe levels for consumers.

They have two coils, a primary and secondary coil, which are joined by an iron core, the number of turns on each coil affects whether the voltage is stepped up or down.

If there are more turns on the secondary coil, the voltage is stepped up, on the other hand, if there are more turns on the primary coil then the voltage is stepped down.

Question 23

What is the equation to calculate the output voltage from a transformer?

Answer 23

Primary voltage / Secondary voltage = Number of turns on primary / Number of turns on secondary

Or

Vp/Vs = Np/Ns

Question 24

How do you calculate power using energy and time?

Answer 24

Power = Energy / Time

Or

W = J/s

Question 25

How do you calculate the cost of using an electrical appliance using power, time in hours and cost of 1kWh?

Answer 25

Cost = Power x Time x Cost of 1kWh

Or

Cost = kW x h x Cost of 1kWh