P15.7 Transformers

Question 1

What is the voltage of your mains electricity?

Answer 1

230V

Question 2

What does a step-up transformer do?

Answer 2

Increases the size of an alternating potential difference

Question 3

What does a step-down transformer do?

Answer 3

Decreases size of alternating potential difference

Question 4

When are step up transformers used?

Answer 4

Used to step up pd from power stations to the National grid

Question 5

How many coils are there in a transformer?

Answer 5

2 coils

Question 6

Why is iron used for the core?

Answer 6

Because iron can easily be magnetised and demagnetised

Question 7

Why is a current induced in the secondary coil?

Answer 7

Alternating current passing through primary coil generates an alternating magnetic field in the iron core

The lines of the alternating magnetic field in the iron cores pass through the secondary coil

The magnetic field in the secondary coil induces an alternating potential difference between the terminals of the secondary coil

Question 8

Why do transformers only work with alternating current not with direct current?

Answer 8

There is no changing magnetic field - so the secondary potential difference is zero