electric and magnetic fields

Question 1

what 2 poles attract

Answer 1

2 opposite poles
(north and south)

Question 2

what 2 poles repel

Answer 2

2 of the same
(north and north OR south and south)

Question 3

what are some examples of magnetic metals

Answer 3

iron
nickel
colbalt
steel

Question 4

what do all the permanent magnetic metals do

Answer 4

attract other magnetic items

Question 5

what do all the temporary magnetic materials do

Answer 5

only become magnetic when placed in a magnetic field and will quickly lose its magnetism when removed from the magnetic field

Question 6

shape of magnetic field in a permanent magnet

Answer 6

from north to south

Question 7

shape of magnetic field in a temporary magnet

Answer 7

same as permanent (north to south) except with a induced magnetic in

Question 8

characteristics of uniform magnetic fields

Answer 8

the magnetic field lines are equidistant and parallel to each other

Question 9

how to use a plotting compass

Answer 9

Put the magnet on a piece of paper and draw round it and place the compass on the paper near the magnet.

The needle will point in the direction of the field line at this position.

Mark the direction of the compass needle by drawing two dots - one at each end of the needle.

Move the compass so that the tail end of the needle is where the tip of the needle was in the previous position and put a dot by the tip of the needle.

Repeat this and then join up the marks you’ve made, you’ll end up with a drawing of one field line around the magnet.

Repeat this method at different points around the magnet to get several field lines.

Question 10

how is there evidence of the earths core being magnetic

Answer 10

when they’re not near a magnet, compasses always point towards the Earth’s North Pole.

this is because the Earth generates its own magnetic field, shows the inside (core) of the Earth must be magnetic.

Question 11

electromagnetism

Answer 11

an interaction that occurs between particles with electric charge via electromagnetic fields.

Question 12

what does the strength of field depend on

Answer 12

size of the current and distance from the long straight conductor

Question 13

real life examples of electromagnets

Answer 13

fridge doors
doorbells
MRI machines

Question 14

explain an electromagnet

Answer 14

has a battery which is connected to wires which are connected to an iron core with wire wrapped around which is connected to the current

Question 15

explain flemings left hand rule

Answer 15

first finger - magnetic field
middle finger - current
thumb - movement

simply line your hand up to the horizontal arrows direction and the vertical direction, that will position your thumb in the correct place

Question 16

what does flemings left hand rule find

Answer 16

the direction of the force on the current carrying conductor

Question 17

what’s the right hand rule and how is it done

Answer 17

point your thumb up in the direction of the current and curl your fingers, direction of fingers is direction of the field

Question 18

what is a solenoid

Answer 18

a long coil of wire with an iron core which is a example of a electromagnet

Question 19

what’s inside a solenoid

Answer 19

individual coils which add together a very strong almost uniform field along the centre of the solenoid and cancel to make the field outside weaker

Question 20

what does a changing magnetic field induce

Answer 20

a potential difference in a conductor

Question 21

what is a step up transformer

Answer 21

step the potential difference up (i.e. increase it)

They have more turns on the secondary coil than the primary coil.

Question 22

what is a step down transformer

Answer 22

step the potential difference down (i.e. decrease it).

They have more turns on the primary coil than the secondary.

Question 23

equation for transformers

Answer 23

Vp x Ip = Vs x Is

Vp - potential difference across primary coil
Ip - current across primary coil

Vs - pd across secondary coil
Is - current through secondary coil

Question 24

explain the national grid

Answer 24

• starts with a power station
• moves into a step up transformer
• then step down transformer
• the home

Question 25

what do transformers in the national gird produce

Answer 25

high P.D. and low current

Question 26

what’s the second transformer equ

Answer 26

Vp / Vs = Np / Ns

Question 27

what so step up and step down transformers do in the nation grid

Answer 27

Step-up transformers at power stations boost the p.d. up really high (400 000 V) and keep the current low.

Step-down fransformers then bring it back down to safe, usable levels at the consumers’ end.

Question 28

what is the national grid

Answer 28

a network of wires and transformers which connect UK power stations to consumers

Question 29

what does the national grid do

Answer 29

transfer loads of energy per second

Question 30

what does the national grid do to reduce losses and make it more efficient

Answer 30

transformers are used

Question 31

what is alternating current (AD)

Answer 31

an electric current that reverses its direction many times a second at regular intervals, typically used in power supplies.

Question 32

what is direct current

Answer 32

an electric current flowing in one direction only.

Question 33

what are magnetic forces due to

Answer 33

interactions between magnetic fields

Question 34

what is flemings left hand rule equation

Answer 34

B x I x L

force:
magnetic flux density x current x length of wire

Question 35

what does current carrying conductors experience

Answer 35

a force that an equal and opposite force acts on

Question 36

what can current create and why

Answer 36

a magnetic effect due to the shape and direction of the magnetic field