Worksheet: Electricity Transmission Networks

In this worksheet, we will practice describing how national electricity grids work and how they respond to changes in demand.

Q1:

What type of device can be used to increase the potential difference of electricity supplied to the national grid so as to increase the power transmitted while reducing energy lost to the surrounding environment?

  • AA transformer
  • BA diode
  • CA rectification circuit
  • DA solenoid
  • EA capacitor

Q2:

The national grid transmits electrical power at a very high potential difference and a very low current. Why is this?

  • AThis occurs because if the current is high, the cables carrying the current heat up, and a lot of power is lost to the surrounding environment. Less energy is wasted by increasing the potential difference and decreasing the current.
  • BThis occurs because most appliances in homes require a very high potential difference and a very low current.
  • CThis occurs because most power stations generate electricity at a very high potential difference, and it is easier to transmit the power with the same potential difference and current that it is generated with.
  • DThis occurs because potential difference can be decreased easily but not increased easily.

Q3:

A nuclear power station in the UK develops a fault and needs to be shut down quickly so that it can be repaired. Which of the following types of power station could be quickly turned on to compensate for the supply lost by the nuclear power station shutting down?

  • AA tidal barrage
  • BA gas-fired power station
  • CA wind farm
  • DA solar farm
  • EAnother nuclear power station

Q4:

Fossil fuel power stations often only produce about 33% of the total electricity they could produce when operating at maximum output. Which two of the following reasons explain why is this?

  1. Because fossil fuel power stations are more efficient when running at far less than their maximum output
  2. So that the national grid can cope with unexpected higher demand
  3. Because we never need more electricity than this
  4. In case there is an unexpected shutdown of another power station
  • Ac and b
  • Bd and c
  • Ca and c
  • Da and b
  • Eb and d

Q5:

Electricity demand increases over winter. Which of the following reasons best explains why this is?

  • APeople stay indoors more in winter and therefore spend more time doing activities that involve electrical appliances, such as watching television.
  • BMany electrical appliances are less efficient in colder temperatures. Thus, a greater electricity supply is needed for the same appliances to work as well.
  • CDuring winter, the weather is colder and it gets darker earlier in the evening. Demand for electricity increases because electrical appliances are being used to heat and light homes for a while longer each day.
  • DElectricity is cheaper in winter, so people switch from heating their homes with gas or oil to heating their homes using electric heaters.

Q6:

The graph shows the power consumption in gigawatts in the UK over a 24-hour period.

Which of the following periods of time during the day was when electricity demand at its lowest?

  • A4:00-8:00
  • B0:00-4:00
  • C12:00-16:00
  • D16:00-20:00
  • E8:00-12:00

Demand for electricity is lower during the night than it is during the day. Which of the following reasons best explains why this is?

  • AElectricity is more expensive at night; therefore, more people turn off electrical appliances to save money.
  • BThe average demand for electricity is lower at night because people are asleep, and thus not using so many electrical appliances.
  • CAt night energy from renewable energy sources, such as solar panels, is lower. This means that a greater proportion of the electricity supply comes from polluting sources, such as coal and natural gas. People turn off their electrical appliances overnight in order to reduce the amount of pollution released into the atmosphere.
  • DMost electrical appliances are more efficient in colder temperatures. As the temperature drops overnight, the total power consumption of the UK drops.

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