Magnetic Fields

Question 1

what is the relation between like and unlike magnetic poles?

Answer 1

• N and N repulsion

- S and N attract- uniform field

Question 2

when drawing magnet poles which was do the arrows go?

Answer 2

north to south

-closer lines together stronger the magnetic field

Question 3

what is a permanent magnet?

Answer 3

• i.e bar magnets

- produce own magnetic field all the time

Question 4

what is a induced (temporary) magnet?

Answer 4

only produce magnetic field while they’re in another magnetic field

Question 5

what are the 3 main magnetic elements?

Answer 5

iron, nickel, cobalt

Question 6

what alloy of the main magnetic elements are magnetic?

Answer 6

steel- alloy of iron

Question 7

how does a compass relate to evidence that the core of the earth must be magnetic?

Answer 7

• always points to north pole

- because earth generates own magnetic field

Question 8

what are permanent magnets?

Answer 8

• eg bar magnets

- produce their own magnetic fields all the time

Question 9

what are induced magnets?

Answer 9

-only produce magnetic field when in another magnetic field

Question 10

what does a moving charge through a long straight conductor (wire) create?

Answer 10

magnetic field

Question 11

how do you work out how large the current is around a wire?

Answer 11

• closer to wire stronger the current

- closer circles are stronger the current

Question 12

what does the right hand thumb rule show you?

Answer 12

the direction of the magnetic field

Question 13

how do you do the right hand tub rule?

Answer 13

thumb points in the way of the current so the fingers follow in the way of the magnetic field

Question 14

what does the strength of the field depend on?

Answer 14

• size of current

- distance form conductor

Question 15

what is solenoid?

Answer 15

long coil of wire

Question 16

what is a solenoid an example of?

Answer 16

an electromagnet

Question 17

what do the individual fields in a solenoid do?

Answer 17

• add to form a strong uniform field along centre

- cancel to give weak field outside the solenoid

Question 18

what happens when a current carrying a conductor is placed near a magnet?

Answer 18

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

Question 19

what are magnetic forces due to ?

Answer 19

magnetic forces are due to interactions between magnetic fields

Question 20

what is Flemmings left hand rule used to show?

Answer 20

represent directions of force, current, and magnetic field

Question 21

how does Flemmings left Hand rule work?

Answer 21

• put first and second finger in an L shape and thumb up
• tumb= motion, force
• first finger= magnetic field
• second finger= current
• fit to a diagram and direct will be given

Question 22

what is the equation to work out the size of a force?

Answer 22

F= B x I x L
force(N)= magnetic density/flux (T) X current(A) X length (m)

Question 23

what are the factors with effects the size and direction of created potential difference?

Answer 23

• increase strength of magnetic field
• more coils
• increase speed

Question 24

how does the magnetic field produced oppose the original change?

Answer 24

• current produces own magnetic field

- magnetic field toys to act against the charge

Question 25

what does induce mean?

Answer 25

create

Question 26

what can a transformer do?

Answer 26

change the size of a alternating voltage

Question 27

what is the national grid?

Answer 27

network of wires and transformers that connect Uk power stations to consumers (anyone who uses electricity)

Question 28

why is energy transferred at different voltages at the national grid?

Answer 28

- high voltage from power stations - lower voltage for domestic use - improves efficiency by reducing heat loss in transmission lines

Question 29

why are step up transformers used in the national grid?

Answer 29

boost p.d. high(400,000V) and keep current low

Question 30

why are step down transformers used in the nation grid?

Answer 30

-bring down to safe and usable levels for consumer

Question 31

what is the equation for transformers which are 100% efficient?

Answer 31

``` Vp X Ip = Vs X Is V= voltage (V) I= current (A) p= primary coil s= secondary coil ```