7.3 Induced potential difference, transformers and the National grid (Triple, Higher)

Question 1

What happens when an electrical conductor moves relative to a magnetic field? (Higher)

Answer 1

A potential difference is induced across the ends of the conductor

Question 2

What happens to an electrical conductor when there is a change to the magnetic field that it is placed in? (Higher)

Answer 2

A potential difference is induced across the ends of the conductor

Question 3

What is the requirement for an induced potential difference to cause a current flow? (Higher)

Answer 3

The conductor must form a closed loop or be part of a complete circuit

Question 4

What can be said about the direction of the magnetic field produced by an induced current? (Higher)

Answer 4

The direction of the current is such that it opposes the change that induced the current. This change is either the movement of the conductor or a change to the field.

Question 5

What are two ways that the generator effect is used to generate different types of current? (Higher)

Answer 5

● In an alternator to produce alternating current

● In a dynamo to produce direct current

Question 6

What electromagnetic effect does a microphone take advantage of and how? (Higher)

Answer 6

The generator effect - it converts the pressure variations in sound waves into alternating current in a circuit.

Question 7

Describe the makeup of a basic transformer. (Higher)

Answer 7

A primary coil and a secondary coil of wire wrapped around an iron core

Question 8

Why is iron used as the core for a transformer? (Higher)

Answer 8

It is easily magnetised

Question 9

Explain how a transformer works. (Higher)

Answer 9

An alternating current flows through the primary coil. This induces a changing magnetic field in the core. This changing magnetic field induces a current to flow in the secondary coil.

Question 10

Why must the current flowing through the primary coil of a transformer be alternating? (Higher)

Answer 10

For current to be induced in the secondary coil, the magnetic field in the core must be continuously changing. For the magnetic field to be changing, the current in the primary coil must be alternating.

Question 11

What can be said about the electrical power input and output of a 100% efficient transformer? (Higher)

Answer 11

The electrical power input is equal to the electrical power output