P2 - Magnetism and Electromagnetism

Question 1

What is a magnetic field ?

Answer 1

A region where other magnets or magnetic materials experience a (non-contact) force.

Question 2

How can you represent a magnetic field ?

Answer 2

By drawing magnetic field lines around the magnet, these always go from north to south and the closer together the lines are the stronger the magnetic field and the further away from the magnet the weaker the field is.

Question 3

Where on a magnet is the magnetic field strongest ?

Answer 3

At the poles (so the magnetic forces here are stronger).

Question 4

How do magnets and magnetic materials interact ?

Answer 4

The force between a magnet and a magnetic material is always attractive, no matter the pole.

Question 5

How do magnetic poles interact ?

Answer 5

If two poles are put near each other they will experience a force, this force will be attractive if the poles are different, and repulsive if the poles are the same.

Question 6

How can you map the magnetic field lines around a magnet ?

Answer 6

You can move a compass around a magnet and trace the needles position of paper to map what the lines look like.

Question 7

How do compasses work ?

Answer 7

Inside there is a small bar magnet with the north pole of this attracted to the south pole of any nearby magnet, if not in the direct force of a magnet they always point north due to earth being magnetic and creating its own magnetic field.

Question 8

What are permanent magnets ?

Answer 8

Ones that produce their own magnetic field.

Question 9

What are induced magnets ?

Answer 9

Magnetic materials that turn into a magnet when they’re put into a magnetic field.

Question 10

What is created when a current flows through a wire ?

Answer 10

A magnetic field around the wire made up of concentric circles perpendicular to the wire.

Question 11

What direction does the magnetic field move in around a wire ?

Answer 11

If the current is flowing towards you then the magnetic field lines will move anti-clockwise (right-hand thumb rule) and changing the direction of current will change the direction of the magnetic field.

Question 12

What effects the strength of the magnetic field around a current carrying wire ?

Answer 12

A larger current will cause a stronger magnetic field, and so will being closer to the wire.

Question 13

What is the right-hand thumb rule ?

Answer 13

Using your right hand point your thumb in the direction of current and curl your fingers, the direction of your fingers is the direction of the field.

Question 14

What is a solenoid ?

Answer 14

A wire wrapped into a coil.

Question 15

Why is the strength of a solenoid greater than that of a wire ?

Answer 15

Because the field lines around each loop of wire line up, all pointing in the same direction and are very close.

Question 16

How does the location around a solenoid affect magnetic field strength ?

Answer 16

Inside the coils of the solenoid it is strong and uniform and outside the coil the magnetic field acts like one around a bar magnet.

Question 17

What is an electromagnet ?

Answer 17

A magnet who’s magnetic field can be turned on and off with an electric current.

Question 18

How can a solenoid be turned into an electromagnet ?

Answer 18

By putting a block of iron in its centre which becomes an induced magnet whenever there’s a current flowing.

Question 19

What are some uses of electromagnets ?

Answer 19

In some cranes to pick up and drop scrap metal in scrap yards, or to act as switches for circuits.

Question 20

What is the motor effect ?

Answer 20

When a current carrying wire is put between magnetic poles the magnetic field around the wire interacts with the magnetic field it’s placed in - causing the magnet and conductor to exert a force on each other. And can cause the wire to move.

Question 21

In what position must the wire be for the motor effect to occur ?

Answer 21

It has to be at 90° to the magnetic field, if it runs parallel to the magnetic field it won’t experience any force and at angles between parallel and perpendicular it will feel some force.

Question 22

In what direction is the resulting force of the motor effect ?

Answer 22

The force always acts at right angles to the magnetic field of the magnets and to the direction of current in the wire.

Question 23

How can you represent the motor effect ?

Answer 23

By applying a current to a set of rails inside a horseshoe magnet and then place a bar on the rails - completing the circuit - which generates a force that rolls the bar along the rails.

Question 24

What is a horseshoe magnet ?

Answer 24

A magnet that folds over itself so the north and south poles are over each other, like a horseshoe shape.

Question 25

How can you increase the magnitude of the force in the motor effect ?

Answer 25

By increasing the strength of the magnetic field or by increasing the amount of current passing through the conductor(can be a wire).

Question 26

P

Answer 26

164