magnetism

Question 1

whats a magnetic compass

Answer 1

• tiny magneti needle pivoted at itsz center
• attracted to the earths mag field so one end always points north and the other south

Question 2

general rule of magets

Answer 2

like poles repel
opposite poles attract

Question 3

what are magnets made of/what can be magnetised

Answer 3

iron
steel
nickel
cobalt

Question 4

what are permenet magnets made of and why

Answer 4

steel because it is hard to demagnetise

Question 5

what is the shape of magnetic field lines

Answer 5

• more concentrated at the more attractive orth and south poles
• curve around
  -always curve from north to south

Question 6

whats a magnetic field and where is it strongest

Answer 6

• region around a maget
• strongest at poles
• distance makes the strength weaker

Question 7

whats induced magetism

Answer 7

• when an unmagnetised magnet is placed in a magnetic field and magnetism is created

Question 8

what else does induced mag cause

Answer 8

• attraction between the nearest poles of the newly magnetised material and the bar maget it has become magnetised by

Question 9

magnetic field near a wire carrying current

Answer 9

• a series of concentric circles
• centered around the wire
• in a plane perpendicular to the wire

Question 10

corkscrew rule

Answer 10

when the current is straight it travels clockwise as it would be if you were screwing down the wire
opposite for reverse as if you are unscrewing

Question 11

whats a solenoid

Answer 11

long coil of insulated wire

Question 12

how does increasing and decreasing the current affect the mag field

Answer 12

• increasing the currnet strengethns
• decreasing reverses the direction of the mag field

Question 13

mag field in a solenoid

Answer 13

• field lines are parrlel to its axis
• all are in the same direction

Question 14

uniform mag field

Answer 14

one where all the mag field lines are parralel and the same direction

Question 15

mag field outside the solenoid

Answer 15

• similar to the circular field of a bar magnet
• each line fully loops around as it passes through the solenoid

Question 16

whats an electromagnet

Answer 16

solenoid where the insulated wire is wrapped around an iron bar
this is induced magnetism and so the unmagnetised iro is magnetised every time the current is switched on

Question 17

the motor effect

Answer 17

a force acts on a magnetised wire in another magnetic field when a current passes through it

Question 18

how can the force in the motor effect be increased

Answer 18

increasing currnet
stregtheing magnet/magnetic field
increasing length of conductor

Question 19

how does the angle effect the size of force i the motor effect

Answer 19

• perpendicar wire to mag field is a greatest force
• parralel wire to mag field means the force is at zero

Question 20

when is a mag field produced

Answer 20

when a current moves through a wire

Question 21

whats magnetic flux density

Answer 21

strentgh of a magnetic field

Question 22

whats mag flux desnity measured in

Answer 22

teslas

Question 23

calculation for the size of the force acting on the wire in the motor effect

Answer 23

F = Mag flux density X current x length

Question 24

flemmings left hsnd rule

Answer 24

thumb = direction of motion
first finger = direction of mag field
second= direction of current

Question 25

what is magneticallly soft

Answer 25

it means you gain and lose magnetism slowly

Question 26

How to increase strength of an electromagnet

Answer 26

You could increase the current,
increase the number of turns of wire while keeping the length of the solenoid the same,
reduce the length of the solenoid while keeping the number of turns of wire the same,
or add a soft iron core.

Question 27

Why is the mag field arohnd a solenoid strong

Answer 27

Mag fields around each turn/coil of a solenoid are lined up closely together

Question 28

Useful properties of electromagnets

Answer 28

• can be switched on and off
• strength of field can be changed by changing currnet

Question 29

electric motor issue

Answer 29

-coil of charged current where the force is both down and up depending on the flow of the current
- the differing forces experiences at either side means it means to spin clockwise
- when it turns 180 it will start turning anti clockwise
- this means it wouldnt ever turn 360

Question 30

how to help e;ectric motor

Answer 30

• change direction of current every 180 turn
• add a split ring commutator which does this through swapping carbon brushes every half turn
• this means that the forces keep acting in the same directuon