P4 - Magnetism

Question 1

1 why were magnets made

Answer 1

originally used to navigate (loadstones)
if they dangle, they point North-South

Question 2

1 what are the 3 magnetic metals

Answer 2

iron (steel has iron in it)
nickel
cobalt

magnetic forces work through non magnetic materials

Question 3

1 what are magnetic forces like

Answer 3

non contact
magnetic field exists around each magnet
strongest force is at each end
north seeking pole
south seeking pole
like magnets REPEL forces
different magnEts ATTRACT forces

Question 4

1 Facts about magnetics fields

Answer 4

the lines dont cross
goes from north to south
touch the magnet
represent magnetic flux
no of lines shows flux density
called magnetic field strength

The top of our planet (north) is really magnetic south!

Question 5

1 facts about compasses

Answer 5

angle between field lines and horizontal to the earths surface is ‘the dip’
90* north and south
0* at the magnetic equator
UK’s field dip is about 70*

Question 6

2 what was discovered by Hans Oersted in 1820

Answer 6

around a current carrying wire there is a magnetic field
increasing the current will increase the magnetic field strength
looping the wire helps to increase strength as well -solenoid

Question 7

2 how can you swap poles on a current carrying wire

Answer 7

revered the current
recoil in reverse the wire

Question 8

2 how can you create an electromagnet from a solenoid

Answer 8

give it an iron core (soft magnetic metal)
to improve the design and create an electromagnet

still works with a steel bar (hard magnetic metal)

Question 9

2 how do you get a stronger electro magnet

Answer 9

increase the current
more coils
wider coils

Question 10

3 what happens when two magnets interact

what is the motor effect

Answer 10

they create a force between them

if you position a wire between two poles of permanent magnet a force will occur when the current is switched on

Question 11

3 what is fleming’s left hand rule?

Answer 11

thumb up
index out
middle to the right

thumb = movement (force)
index = magnetic field
middle = current

Question 12

3 how do you increase force

Answer 12

increase current
more magnetism
more wire inside magnetic field

Question 13

3 equation for force on a wire

Answer 13

force magnetic length
on a = field x current x of
wire strength wire

force = N
magnet = Tesla, T
current = A
length = m

Question 14

4 how do you create a motor effect?

Answer 14

use a force on a wire to create a spinning motion

Question 15

4 how does a motor spin faster

how do you reverse the motor

Answer 15

strong magnets
increase current/voltage
more coils
insert an iron core

reverse current flow
swap magnetic poles around

Question 16

4 what is a commutator

Answer 16

part with the split ring and brass contacts that connect the power supply to the coil

allows coil to spin freely and not get caught up

also swaps the current directions in the coil every turn so each side gets the correct push as it reconnects