Electromagnetism

Question 1

Magnetic compass contains

Answer 1

A small bar magnet that points in the direction of the magnetic field of the earth.

Question 2

Permanent vs induced magnet

Answer 2

Permanent magnet produces its own magnetic field

An induced magnetic become a magnet when placed in a magnetic field

Question 3

Magnetic field

Answer 3

The region surrounding a magnet where another magnet or magnetic material experience a contact force.

Question 4

What is produced when a current flows through a conducing wire

Answer 4

A magnetic field is produced around the wire

Question 5

What determines strength of magnetic field around a current carrying wire

Answer 5

The magnitude of current flowing through the wire

The distance from wire

Question 6

Solenoid

Answer 6

A coil of wire when current passes through creates a strong magnetic field

Question 7

Electromagnet

Answer 7

A solenoid with an added iron core

Adding iron core increases strength of magnetic field

Question 8

Motor effect

Answer 8

When a force is exerted between a magnetic field and a current carrying conductor placed in that field

Question 9

Flemmings left hand rule

Answer 9

Thumb - movement
Forefinger - field
Second finger - current

Question 10

Factors that affect the size of force on a current carrying wire in a magnetic field

Answer 10

Magnitude of current flowing through conductor

Strength of magnetic field conductor is placed in

Question 11

How does an electric motor work

Answer 11

A coil of wire carrying a current is placed in a magnetic field

The forces on two sides perpendicular to the field experience forces in opposite directions

This cause a rotational effect

Question 12

How do loudspeakers make use of motor effect

Answer 12

The motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound.

Question 13

How do loud speakers work?

Answer 13

• A cone with a wire wrapped around it is connected to an
a.c power supply and is placed in a permanent magnetic field
• When current flows through the wire, it creates a second magnetic field, which interacts with the permanent field
• This produces a force which causes the cone to vibrate

Question 14

Electrical conductor moves relative to a magnetic field

Answer 14

A potential difference is induced across ends of conductors

Question 15

Electrical conductor when there is a change to magnetic field

Answer 15

A potential difference is induced across the ends of conductors

Question 16

Requirement for induced potential difference to cause a current flow

Answer 16

Conductor must for a close loop or be part of complete circuit

Question 17

What can be said about direction of the magnetic field produced by an induced current

Answer 17

The direction of a field is such that it opposes the change that induced the current

The change is either movement of conductor or change of the field

Question 18

Generator effect is used to generate different types of current

Answer 18

In an alternator to produce alternating current

In dynamo to produce direct current