F - Electromagnetism

Question 1

A straight wire carrying an electric current has a circular ___________________ around it.

Answer 1

magnetic field

Question 2

How does the magnetic field around a straight wire look?

Answer 2

The field around a straight wire forms concentric circles

Question 3

What happens to the magnetic field aroud the wire if we reverse the current on a wire

Answer 3

It changes direction/ reverses

Question 4

How does the field around a single flat coil or loop of wire look?

Answer 4

The field produced round a single flat coil or loop of wire looks like:

Question 5

How does the magnetic field around a solenoid look?

Question 6

If we place a conductor (a wire or metal) inside a magnetic field then something amazing happens – what?

Answer 6

The conductor (wire) moves

Question 7

Explain what the motor effect is

Answer 7

If a current carrying wire is placed in a magnetic field it experiences a force and moves.

Question 8

For a current carrying wire in a magnetic field to experience the maximum force, it has to be————to the magnetic field.

Answer 8

At right angles/ perpendicular

Question 9

Where does your thumb point in Flemings left hand rule?

Answer 9

Thrust, movement, force.The direction the wire will move if placed in a magneti field.

Question 10

What does your first finger point to in Flemings left hand rule.

Answer 10

Field - magnetic field. From North to South.

Question 11

Where does your second finger point in Flemings left hand rule?

Answer 11

Current

Question 12

What happens to the force on the motor effect if the wire is made into a coil?

Answer 12

A turning force is produced if the wire is made into a coil. This effect is used in simple DC (direct current) electric motors.

Question 13

Name 3 things which use an electric motor?

Answer 13

• fans
• electric drills
• food processors
• washing machines
• CD and DVD players

Question 14

How does a simple dc motor work?

Answer 14

When a current carrying coil is placed in a magnetic field it will rotate	the current flowing through the coil creates a magnetic field	the field around the current interacts with the field produced by the magnet	the forces combine to make the coil rotate

Question 15

How can you increase the speed of a motor?

Answer 15

increase the size of the magnetic field	increase the size of the current	increase the number of turns on the coil

Question 16

What is a split-ring commutator?

Answer 16

Is used in an electric motor to change the direction of current every half turn to keep the coil rotating.

Question 17

What is electromagnetic induction?

Answer 17

When a magnet is moved into a conductor (such as a coil of wire) a current will be induced.

Question 18

How can you increase the size of the voltage induced by electromagnetic induction (such as in a generator)?

Answer 18

increase the strength of the magnetic field	increase the speed of rotation of the magnet	increase the number of coils	add iron core inside coil