The National Grid

Question 1

What is the national grid?

Answer 1

a system of cables and transformers linking

power stations to consumers.

Question 2

what does the national grid transfer?

Answer 2

electrical power from power stations anywhere on the grid(the supply)to anywhere else on the grid where it’s needed(the demand)-homes and industry

Question 3

why do power stations often run below their maximum power output?

Answer 3

so there’s spare capacity to cope with a high demand,even if there’s an unexpected shut-down of another station.

Question 4

to transmit huge amount of power what is needed?

Answer 4

a high potential difference or a high current.

P=VI

Question 5

What is the problem with high currents?

Answer 5

you lose loads of energy as the wires start to heat up and energy is transferred to the thermal energy store of the surroundings

Question 6

How does the national grid make an efficient way of transferring energy?

Answer 6

the pd is increased which decreases the current,which then decreases the energy lost by heating the wires and the surroundings.

Question 7

What is used to get the pd to 400 000V for an efficient transmission?

Answer 7

transformers

Question 8

what do all transformers have?

Answer 8

a primary and secondary coil,joined with an iron core

Question 9

why are step-up transformers used?

Answer 9

to increase the potential difference from the power station to the transmission cables

Question 10

why is the step-down transformer used?

Answer 10

to decrease, to a much lower value, the potential difference for domestic use.

Question 11

what is the power given of a primary coil?

Answer 11

by power=pd*current

Question 12

what does it mean if transformers are 100% efficient?

Answer 12

power in primary coil=power in secondary coil