Energy,electricity and fuels

Question 1

Negatives of photocells

Answer 1

Expensive to buy

No power at night or in bad weather

Question 2

How do photocells work

What does the power of the photocell depend on

Answer 2

Sun’s energy is absorbed causing electrons to be knocked loose from silicon crystals
These electrons flow freely as ELECTRIC CURRENT charge
It transfers light energy into an electric DC current

Question 3

Why are photocells good for capturing maximum light energy
How can they be used to capture more sunlight

What current to they use

Answer 3

Photocells have a flat surface
They can be joined together to create larger surface area, more energy

Photocells use DC current that travels in the same direction all the time

Question 4

What does power output of photocell depend on

Answer 4

Power output depends on light intensity,surface area and distance from light source

Question 5

How can solar panels be used to heat water for washing and heating buildings

Answer 5

Sunlight absorbed by panel transfers to heat energy

Water passed over this heats up

Question 6

Positives of photocells

Answer 6

Little maintainance
Operate in remote locations
No fuel or power cables
Uses renewable energy source
No pollution or waste

Question 8

What can glass provide for heating buildings

Answer 8

Passive solar heating, this traps sun energy but won’t distribute or change it into another form of energy

Question 9

Curved mirror

Answer 9

Focuses sunlight to heat up a solar panel

Question 10

How do windows heat up rooms

Answer 10

Light passes straight through windows
It is absorbed by objects in the room
They emit infrared radiation (longer wavelength than visible light) which is reflected back into the room by the glass so cant escape
Room warms up

Question 11

Solar collector and why is it used

Answer 11

A solar collector can track the sun to maximise power output

requires extra technology and therefore cost

Question 12

Why can light pass straight through glass

Answer 12

Glass is transparent to some wavelengths of sun’s radiation,including visible light so light passes straight through glass windows

Question 13

How is energy generated in a dynamo

What kind of circuit is this

Answer 13

By moving a wire near a magnet/ magnet near a wire

The wire cuts through the lines of force of the magnetic field and a current is produced in the wire

This is a complete circuit

Question 14

How can you increase current produced in a dynamo

Answer 14

A stronger magnet
Moving wire/magnet faster
Adding more turns of wire on the coil

Question 15

How do wind turbines work

Answer 15

Sun heats the air producing convection currents-wind
They turn the turbines
Turbines transfer kinetic energy into electrical energy

Question 16

Positives and negatives of wind turbines

Answer 16

Renewable energy source
No chemical pollution or waste

Needs space and windy region
Dependant on wind
Visual pollution due to size

Question 17

Why do generators use the dynamo effect

Answer 17

Generators produce alternating current AC
so direction of current is continually alternating every time magnet/coil changes direction

Batteries produce DC

Question 18

Generators produce an Alternating Current

Describe this

Answer 18

The direction of the current continually alternates, every time the magnet or coil changes direction

The voltage generated changes direction causing current to change direction

Question 19

What do consumers access electricity through

Answer 19

The national grid

Question 20

How do fossil fuels being burnt produce electricity in the national grid

Answer 20

Fossil fuels are burned to release heat energy 
Heat energy boils water to produce steam
Steam rotates turbines
Turbines turn generators
Electricity is produced

Question 21

How is producing electricity for the national grid different to a nuclear power station

Answer 21

Fuel rods of uranium release energy as heat to make steam in the power station

Question 22

How can biomass be used to produce electricity

Answer 22

Biomass eg. wood can be burned or fermented to generate methane
Methane can be burned in the power station

The biomass absorbs carbon dioxide then releases it when burnt
Biomass needs lots of land

Question 23

What is electric current

Answer 23

Flow of electric charge, transfers energy from power supply to the components in the circuit

Question 24

What are Watts

Answer 24

1 watt is the transfer of 1J of energy per second

Question 25

What is off peak electric

Answer 25

A company can sell the electricity they generate so they don’t have to turn off power stations

For the user off peak is more economical
For producer off peak is less economical

Question 26

What can off-peak electricity be used for

Answer 26

Heating water and storage heaters

Powers washing machines and dishwashers at night

Question 27

The number of units of electricity used by appliances depends on

Answer 27

Power rating in kilowatts

Time in hours it is switched on for

Question 28

How do you calculate the cost of using a device

kWh

Answer 28

Number of kilowatt hours (kWh)= power rating(kW) X time (h)

Total cost= number of kW hours(kWh) X cost of one kWh

Question 29

What is current fed through (in the National grid) to supply electricity to homes efficiently with electricity

What does this do

Answer 29

Transformers change voltage of alternating currents
They increase voltage of supply and at the same time, reduce current

Increasing voltage reduces energy lost as heat (through heating) during electricity transmission, so reduces costs

Question 29

Batteries and photocells produce an Direct Current

Describe this

Answer 29

Electric current flowing in only one direction