Section 22 - Magnetic fields - Permanent and induced magnets, magnetic fields, electromagnetism and the Motor Effect (Not finished)

Question 1

When drawing magnetic field lines, which direction do the arrow lines go and what does this show?

Answer 1

Always go from north to south and they show which way a force would act on a north pole at that point in the field

Question 2

What is a uniform magnetic field?

Answer 2

When magnetic field lines are same distance apart from each other and parallel between opposite poles. Magnetic field is same strength everywhere between poles

Question 3

How is the inside (core) of the earth magnetic?

Answer 3

Compasses always point towards the North Pole as the earth generates its own magnetic field

Question 4

Name three main magnetic elements?

Answer 4

Iron, nickel and cobalt as well as alloys of these metals

Question 5

Difference between permanent and induced magnets?

Answer 5

Permanent - produce their own magnetic fields all the time (e.g. bar magnets)
Induced (or temporary) - only produce a magnetic field while they’re in another magnetic field (e.g. putting magnetic material into a magnetic field, it becomes an induced magnet)

Question 6

Which magnetic material lose their magnetism quickest?

Answer 6

Magnetically ‘soft’ materials lose their magnetism very quickly whilst magnetically ‘hard’ materials lose their magnetism more slowly

Question 7

7 examples of uses of magnetic materials?

Answer 7

Fridge doors, cranes, doorbells, magnetic separators, maglev trains, MRI machines, speakers

Question 8

What is created when a current flows through a long, straight conductor?

Answer 8

A magnetic field around it

Question 9

What does the right-hand thumb rule represent?

Answer 9

Thumb represents current and fingers in coil represent the magnetic field in that direction

Question 10

What happens when a current-carrying conductor is put between magnetic poles?

Answer 10

When a current-carrying conductor is put between magnetic poles, the two magnetic fields interact with the result is a force on the wire

Question 11

What is Fleming’s left-hand rule used to find and what does it represent?

Answer 11

Used to find direction of force on a current-carrying conductor
ThuMb represents direction of force (Motion), First finger represents direction of magnetic Field, and seCond finger represents direction of Current

Question 12

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

Answer 12

Magnetic flux density - how many field (flux) lines there are in a region. Shows strength of magnetic field
Size of current through conductor
Length of conductor that’s in magnetic field

Question 13

Equation for force acting on conductor when current is at 90º to magnetic field it is in?

Answer 13

Force (N) = magnetic flux density (T,tesla or N/Am) x Current (A) x length (m)
F = B x I x l(ength)