Magnetism And The Motor Effect

Question 1

What poles attract and what poles repel

Answer 1

Unlike magnetic poles attract

Like magnetic poles repel

Question 2

What are some uses of permanent magnets

Answer 2

Fridge doors

Question 3

What are some uses of induced magnets

Answer 3

Cranes,

Question 4

What id the difference between permanent and induced magnets

Answer 4

Permanent magnets produce a magnetic field all the time, induced magnets only produce a magnetic field when they’re in another magnetic field

Question 5

What is the shape and direction of the magnetic field around a bar magnet like

Answer 5

They have field lines around the magnet always going from north to south and they show which way a force would act on a North Pole at that point in the field

Question 6

What are some permanent magnetic materials

Answer 6

Iron, nickel, cobalt, steel

Question 7

What is the shape and direction of the magnetic field around a uniform field like

Answer 7

You draw at least 3 field lines parallel to each other and the same distance apart

Question 8

What is a uniform field

Answer 8

When u place the north and south poles of 2 bar magnets near each other creates a uniform field between the poles, the magnetic field is the same strength everywhere between the poles

Question 9

Steps of using a plotting compass to show the shape and direction of the field on a magnet

Answer 9

1) place the magnet on a piece of paper and draw round it
2) places compass on the paper near the magnet -needle will point in the direction of the field line at this position
3) mark the direction of the compass needle by drawing 2 dots one at each end of the needle
4) then move the compass so the tail end of the needle is where the tip of the needle was in the previous position and put a dot by the tip of the needle
5) repeat this and then join up the marks made, repeat these steps in diff positions to get several field lines

Question 10

Where do compasses point when they’re not near a magnet and why

Answer 10

Towards the earths North Pole, because the earth generates its own magnetic field - shows the earth core must be magnetic

Question 11

What does the strength of the field depend on

Answer 11

The size of the current and the distance from the long straight conductor

Question 12

What does a current carrying conductor placed near a magnet experience

Answer 12

A force that an equal and opposite forces acts on the magnet

Question 13

What are magnetic forces due to

Answer 13

Interactions between magnetic fields

Question 14

How does the inside of a solenoids fields from individual coils add together to form a very strong almost uniform field along the centre of the solenoid

Answer 14

Inside the solenoid, u get lots of field lines pointing in the same direction. Magnetic field=strong and almost uniform

Question 15

How does the inside of a solenoids fields from individual coils cancel to give a easier field outside the solenoid

Answer 15

Outside the coil, the overlapping field lines cancel each other out so the field is weak apart from the ends of the solenoid

Question 16

What is magnetic flux density measured in

Answer 16

Tesla(T) or newton per ampere (N/A)

Question 17

What happens if there is a change in direction of the current

Answer 17

It changes the direction of the magnetic field

Question 18

WHat does a change in the direction of the current or magnetic field result in

Answer 18

Change in the direction of the force

Question 19

What does Flemings left hand rule used for

Answer 19

Used to find the direction of the force on a current-carrying conductor

Question 20

Steps on using Flemings left hand rule

Answer 20

1) use your left hand, point your First finger in the direction of the magnetic Field and your seCond finger in the direction of the Current
3) your thuMb will then point in the direction of the force (Motion)

Question 21

What 3 things does the force acting on a conductor in a magnetic field depend on

Answer 21

1) the magnetic flux density-how many field(flux) lines there are in a region
2) size of the current through the conductor
3) the length of thr conductor that’s in the magnetic field

Question 22

When can this equation be used F=B x I x L

Answer 22

When the current is at a 90° to the magnetic field it is in

Question 23

What factors affect size and direction of induced p.d

Answer 23

Strength of magnetic field, speed of movement/change of field, turns per unit length of coil of wire

Question 24

How can an alternating current in one circuit induce a current in another circuit in a transformer

Question 25

What can a transformer change

Answer 25

The size of an alternating voltage