Electromagnetism

A current carrying wire is surrounded by:

• 1 A gravitational field only
• 2 A magnetic field
• 3 Nothing
• 4 A sound field

A device that converts mechanical energy into electrical energy is a:

• 1 Battery
• 2 Transformer
• 3 Motor
• 4 Generator

A transformer works on the principle of:

• 1 Reflection
• 2 Mutual induction
• 3 Friction
• 4 Refraction

A step up transformer has:

• 1 More turns in the primary
• 2 More turns in the secondary
• 3 No core
• 4 Equal turns

A transformer has 100 primary turns, 500 secondary turns and a 20 V input. What is the output voltage?

• 1 100 V
• 2 20 V
• 3 500 V
• 4 4 V

The magnetic field lines outside a bar magnet go from the:

• 1 South pole to the north pole
• 2 Centre to the south pole
• 3 North pole to the south pole
• 4 Centre to the north pole

A coil in a magnetic field carrying current experiences:

• 1 A sound
• 2 A cooling effect
• 3 No force
• 4 A turning force

An electric motor changes:

• 1 Mechanical into electrical
• 2 Heat into light
• 3 Sound into light
• 4 Electrical energy into mechanical energy

The core of a transformer is made of soft iron because it:

• 1 Is easily magnetised and demagnetised
• 2 Is a poor conductor
• 3 Is cheap only
• 4 Is lighter