Lesson 7: Tranformers

Question 1

What are the 3 main components of a basic transformer?

Answer 1

1.) Primary coil.
2.) Secondary coil
3.) Iron core.

Question 2

Why is iron used in transformers?

Answer 2

• Because, it is easily magnetised.

Question 3

If transformers were 100% efficient, what would be the relationship between the power input and power output of the transformer?

Answer 3

• Power input and power output would be equal.
• Vs × Is = Vp x Ip
  s = secondary coil
  p = primary coil

Question 4

Explain why there is an alternating current in the output when the transformer is connected to a circuit.

Answer 4

1.) Primary coil is connected to alternating current.
2.) The alternating current (in the primary coil) generates a changing magnetic field.
3.) Creates magnetic field that changes direction (in the core.)
4.) This induces an alternating potential difference across the secondary coil - causing an alternating current.

Question 5

What is the difference between a step up and step down transformer (in terms of number of turns on primary/ secondary coils?)

Answer 5

• Step up transformer: more turns on secondary coil.
• Step down transformer: more turns on primary coil.

Question 6

What is the potential difference across primary/ across secondary coil like in step up transformer?

Answer 6

Vs > Vp

Question 7

What is the potential difference across primary/ across secondary coil like in step down transformer?

Answer 7

Vs < Vp

Question 8

What is the advantage of power being transmitted (in the National Grid) at high potential differences?

Answer 8

• Less current = less heat lost to the surroundings.