Magnetism and the motor effect

Question 1

What are permanent magnets

Answer 1

Always are magnetic and always have poles

Question 2

List 4 magnetic materials

Answer 2

1. Cobalt
2. Steel
3. Nickel
4. Iron

Question 3

What is induced magnetism

Answer 3

When an object becomes a temporary magnet in the presence of a magnetic field

Question 4

Describe the shape and direction of a magnetic field

Answer 4

1. Field lines point north to south
2. Field strength decreases with distance from the magnet
3. Direction points towards to south and away from north

Question 5

What is the role of a plotting compass

Answer 5

They show the direction and shape of a magnetic field at any given point

Question 6

How do compasses show that the earth’s core contains magnetic fields

Answer 6

The needle of a compass points in the direction of Earth’s magnetic field (the core of the earth) which is made of iron which is a magnetic material

Question 7

Describe how to show that a current can create a magnetic effect around a long straight conductor

Answer 7

When a current flows in a wire it creates a circular magnetic field around the wire which is perpendicular to the conductor.

Question 8

What does the strength of a magnetic field depend on

Answer 8

• Current size (greater the current, stronger the magnetic field)
• Distance from the conductor (Greater the distance weaker the field)

Question 9

What is a solenoid

Answer 9

a coil of wire that acts like a magnet when carrying a current

Question 10

How do solenoids add up to form a very strong almost uniform field

Answer 10

small magnetic fields caused by the current in each coil add together to make a stronger overall magnetic field.

Question 11

Why are solenoids weaker on the outside

Answer 11

magnetic fields caused by the current in each coil cancel each other out

Question 12

What is the benefit of an iron core within a solenoid

Answer 12

increases its strength of the fields as it is easier for magnetic field lines to pass through than air

Question 13

What happens when a wire with a current is placed near a magnet

Answer 13

• experiences a force
• an equal and opposite forces acts on the magnet.

Question 14

What happens when a current flows through a long straight conductor

Answer 14

creates a circular magnetic field around the wire.

Question 15

How are magnetic forces due to interactions between magnetic fields

Answer 15

• The magnetic field around a wire is circular
• Magnetic field between two magnets is straight
• When they interact, the wire will be pushed away from the field between the poles (at right angles to the wire direction and the field direction)

Question 16

What does your thumb show in fleming’s left hand rule

Answer 16

Motion/ force

Question 17

What does your index finger show in Fleming’s left hand rule

Answer 17

Field

Question 18

What does your middle finger show in Flemings left hand rule

Answer 18

Current

Question 19

how is the force on a conductor in a magnetic field used to cause rotation in electric motors

Answer 19

1. When two magnets are placed close to each other, the magnetic fields affect each other
2. If a wire carrying a current is placed inside this magnetic field, a force is produced.
3. Direction of the force will depend on the direction of the magnetic field and the direction of the current in the field