Power and paying for electricity

Question 1

Equation for power

Answer 1

power = voltage x current

Question 2

Equation for energy transfer

Answer 2

energy transferred = power x time

Question 3

Equation for cost of energy supplied

Answer 3

cost = energy transferred x cost per unit

Question 4

What is a step-up transformer?

Answer 4

Device that increases the voltage of an electricity supply

Question 5

What is a step-down transformer?

Answer 5

Device that reduces the voltage of an electricity supply

Question 6

What is an electricity substation?

Answer 6

Place that contains one or more transformers

Question 7

Why does the National Grid use high voltage transmission?

Answer 7

When a current flows through a wire, there is a heating effect and this dissipates some energy. The larger the current, the more heat is produced, and the more energy is wasted. Using the equation, you can see that for a given power, if you increase the voltage, the current decreases. This reduces the amount of energy wasted in the power lines.

Question 8

Off-peak electricity

Answer 8

Electricity can be cheaper at night if you have off-peak electricity. Some people take advantage of this cheaper electricity and heat their homes and water using off-peak electricity. Some people also set their washing machines to run when off-peak electricity is available.