P7 Magnetism and electromagnetism

Question 1

If two permanent magnets are brought together North to North what will happen?

Answer 1

They will repel

Question 2

If two permanent magnets are brought together North to South what will happen?

Answer 2

They will attract

Question 3

What is an induced magnet?

Answer 3

An induced magnet is a material that becomes a magnet when it is placed in a magnetic field

Question 4

What force does induced magnetism always produce?

Answer 4

An attraction force between as there induce magnetism is always the opposite way around to the original magnetism (poles are reversed)

Question 5

What happens to an induced magnet when it is removed from the magnetic field causing it?

Answer 5

Once removed from the magnetic field causing it an induced magnet will rapidly lose most / all of its magnetism

Question 6

What is a magnetic field?

Answer 6

It is the area around a magnet where a force acts on another magnet or magnetic material (iron, steel, cobalt, nickel)

Question 7

What is always true about the force between a magnet and a magnetic material?

Answer 7

it is always an force of attraction

Question 8

Where is the force of a magnet strongest?

Answer 8

At the poles

Question 9

What factor affects the strength of a magnetic field?

Answer 9

The distance from the magnet

Question 10

How do you work out the direction of a magnetic field at any point?

Answer 10

The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point.

Question 11

Which way do magnetic field lines point?

Answer 11

The direction of a magnetic field line is from the north

(seeking) pole of a magnet to the south(seeking) pole of the magnet.

Question 12

How does a compass work?

Answer 12

The compass needle points in the direction of the

Earth’s magnetic field.

Question 13

How can you plot the magnetic field of a bar magnet using a small compass?

Answer 13

Put the compass at a point by the magnet. Mark the position that the north seeking pole points to and the position that the south seeking pole points to. Then position the compass at each of these new points and repeat until both ends connect to the magnet. Join the field lines from the south (seeking pole) to the north (seeking pole) of the permanent magnet

Question 14

What effect does a current flowing through a wire cause?

Answer 14

When a current flows through a conducting wire a magnetic field is produced around the wire.

Question 15

What two factors affect the strength of an electromagnet?

Answer 15

The strength of the magnetic field depends on the current through the wire and the distance from the wire

Question 16

Why are wires used for electromagnets shaped as coils?

Answer 16

Shaping a wire to form a solenoid increases the strength of the magnetic field created by a current through the wire.

Question 17

What do you know about the magnetic field inside a solenoid?

Answer 17

The magnetic field inside a solenoid is strong and uniform.

Question 18

What effect does adding an iron core have on an electromagnet?

Answer 18

Adding an iron core increases the strength of the

magnetic field of a solenoid.

Question 19

What is an electromagnet?

Answer 19

An electromagnet is a solenoid with an

iron core

Question 20

HT ONLY

What is Flemming’s left hand rule?

Answer 20

When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other. This is called the motor effect. Flemming’s left hand rule shows the direction of Motion (thuMb), magnetic Field (First finger) and Current (seCond finger)

Question 21

What is the equation that links force, current, length and magnetic flux density?

Answer 21

f orce = magnetic f lux densit y × current × length