P12

Question 1

permannent magnets

Answer 1

made from mag material(iron)
always causes a force o other msgnets
produces own mag field
mag field cannot be turned off
bar magnets and horchoe magnets examples

Question 2

induced magnets

Answer 2

only becomes a magnet in a magnetic field
induced magnetism is quickly lost when magnet remved from the field
iron filings

Question 3

shape and direction of magnetic field bar magnets

Answer 3

mag fields line never cross each other
closer lines=syronger mag field
have arrows to show direction of force exerted on magnetic north
arrows point from north pole to south pole

Question 4

how behaviour of msgnetic compass shpowsnthat the earth core is magnetic

Answer 4

suggests has a magnetic field and a magnetic core made from iron and nickel

Question 5

mag field aeround wire (current)

Answer 5

-when current flows in a wire, creates mag field around the wire
-strength of field is greater closer to the wire and increases if the current increases
direction of current and mag field with right hand rule
coil fingers of right hand
with thumb pointing away frim hand
thumb=current
finger-direction of mag field

Question 6

how inside a solenoid the field from individual coils
sum to form very strong almost uniform field along the centre of the solenoid
cancel to give a weakerf ield outside the solenoid

Answer 6

is a wire coiled up into spiral shape
whe current flows, solenoid acts as an electromagnet
shape iof mag field very saimilar to one of a mag
fiedl=strong and unifrom
small mag fields in each coil add to be a stronger overall mag field
outside, the smaller mag fields from each wire cancel each orther out and outside fiekd is much weaker
electromagnets used in
door locks that can be controlled remotely and electric bells

Question 7

what does a current carrying conductor placed near a magnet experience

Answer 7

a force and an equal and opposite force acts on the magnet

Question 8

what are magnetic forces due to

Answer 8

interactions between magnetic fields

Question 9

fkemings’s left hand rule

Answer 9

hold thumb, forefinger and second finger at right angle to each other
forefinger-mag fields from north to sputh
2nd finger-current from pos to neg
thumb-direction of motor effect force on the conductor carrying the current

Question 10

equation for force on a conductor at right angles to a magnetic field carrying a current

Answer 10

=magnetic flux density (tesla)(mewton per ampere metre) x current(a) x length (m)

Question 11

how force on a conductor in a mag field is used to cause rotatiom in electrical motors

Answer 11

mag field interacts with a 2nd mag field causing a force to be exerted
forces acting on a coil of wire in a mag field will cuase it to rotate
this rotation is used inside an electric motor