3.2.2 Transformers

Question 1

What happens if a electrical conductor cuts through a magnetic field?

Answer 1

If an electrical conductor ‘cuts’ through a magnetic
field a potential difference is induced across the
ends of the conductor.

Question 2

How can a magnetic field be induced across a coil of wire?

Answer 2

f a magnet is moved into a coil of wire a potential

difference is induced across the ends of the coil.

Question 3

Explain how a p.d is induced across the secondary coil.

Answer 3

An alternating current in the primary coil produces
a changing magnetic field in the iron core and
hence in the secondary coil. This induces an
alternating potential difference across the ends
of the secondary coil.

Question 4

What is a step up transformer?

Answer 4

In a step-up transformer the potential difference
across the secondary coil is greater than the
potential difference across the primary coil.

Question 5

What is a step down transformer?

Answer 5

In a step-down transformer the potential difference
across the secondary coil is less than the potential
difference across the primary coil

Question 6

What frequency do switch mode transformers operate on?

Answer 6

Switch mode transformers operate at a high

frequency, often between 50 kHz and 200 kHz.

Question 7

List some features of switch mode transformers.

Answer 7

Switch mode transformers are much lighter and
smaller than traditional transformers working from
a 50 Hz mains supply.
Switch mode transformers use very little power
when they are switched on but no load is applied.