P15

Question 1

All magnets produce a magnetic field

Answer 1

A region where other magnets or magnetic materials experience a force.

Question 2

The lines on a mgneric field diagram only go from

Answer 2

North to south

Question 3

The closer the lines are together,

Answer 3

The stronger the magnetic field. The further away from a magnet you get, the weaker the field is

Question 4

The magnetic fiekd is strongest

Answer 4

.at the poles of a magnet. This means that the magnetic forces are also strongest at the poles.

Question 5

The force between a magnet and a magnetic material is always

Answer 5

attractive, mo matter the pole.

Question 6

If two poles of a magnet are put near each other

Answer 6

They will each exert a force on each other. The force csn be attractive or repulsive. Two poles that are the same will repel each other, two unlike poles will attract each other

Question 7

What are the gs that can effect the power of the electromagnet

Answer 7

• the core material
• number of coils
• size of the current

Question 8

Inside a compass is a tiny

Answer 8

• ## Bar magnet. The north pole of this magnet is attracted to the south pole of any other magnet it is near.

Question 9

You can move a compass around a magnet and trace

Answer 9

Its position on some paper to build up a picture of what the magnetic field it is in

Question 10

When they aren’t near a compass

Answer 10

It always points north. This is because the earth generates its own magnetic field, which shows the inside of the earth must be magnetic

Question 11

There are two types of magnet

Answer 11

Permanent and induced

Question 12

Permanent magnet

Answer 12

Produce their own magnetic field

Question 13

Induced magnets

Answer 13

Are magnetic materials that turn into a magnet when they’re put into a magnetic field.
The force between permanent and induced magnets is always attractive.

Question 14

When you take away the magnetic field, Induced magnets

Answer 14

quickly lose their magnestusn and stop producing a magnetic field

Question 15

Slide 12 on 15.1 for diagram

Answer 15

1. When the current flows through the
   circuit, the electromagnet makes a
   magnetic field.
2. The electromagnet attracts the
   springy metal arm.
3. The arm hits the gong, which
   makes a sound.
4. The circuit is broken now the arm is
   out of position.
5. The electromagnet is turned off and
   the springy metal arm moves back.
6. The circuit is complete again.
7. The cycle repeats as long as the
   switch is closed.

Question 16

When a current flows through a wire

Answer 16

A magnetic field is created around the wire.
- the field is made up of concentric circles perdendicular to wire with wire in middle (cgp 93)
- you can see this by placing a compass near a wire, that is carrying a current. As u move the compass, it will trace the direction of the magnetic field

Question 17

When a current-carrying wire is put between magnetic poles, the magnetic field around the wire interacts with rhe magnetic field it has been placed in. This causes the magnet and the conductornto exert a force on each other. This isncalled the

Answer 17

Motor effect and and can cause the wire to move.

Question 18

Force, magnetic flux density, length, current

Answer 18

Force (N) = magnetic flux density (T,tesla) x Current (A) x length(m)
F. =. B. X. i. X. L

Question 19

How does a motor work?

Answer 19

Forces act on the two side arms of a coil of wire that’s carrying a current. These forces are just the usual forces which act on any current in a magnetic field. Because the coil is on a spindle and the forces act one up and one down, it rotates. The split-ring commutator is a clever way of swapping the contacts every half turn to keep the motor rotating in the same direction. The direction of the motor can be reversed either by swapping the polarity of the dc supply (reversing the current) or swapping rhe magnetic ooles over (reversing the field).

Question 20

Generator effect

Answer 20

The induction of a pd (and current if there’s a complete circuit) in a wire which is moving relative to a magnetic field, or experiencing a change in magnetic field.

Question 21

The generator effect, how to get it

Answer 21

You can do thid by moving s mahnet in a coul of wire or moving a conductor in a magnetic field. Shfiting the magnet from side to side creates a little blip of current if the conductor is part of a complete circuit.
If you move the magnet in the opposite direcrion, then the pd/currentwill be reversed. Likewise if the polarity or the magnet is reversed, then the potential difference /current will be reversed too.
If you keep the magnet moving backwards and forwards, you produce a potential difference that keeps swapping direction- an alternating current.
- no current is generated when wire is stationary.

Question 22

If your looking at a solenoid end and the current is clockwise, the pole is

Answer 22

South

Question 23

If your looking at the end of the solenoid, and the current is travelling anticlockwise

Answer 23

Its at the north pole

Question 24

STEP-UP TRANSFORMERS

Answer 24

Step the potential difference up. They have more turns on the secondary coil than the primary coil

Question 25

STEP-DOWN TRANSFORMERSA

Answer 25

Step the potential difference down. They have more turns on the primary coil than the secondary.