Magnetism and electromagnets

Question 1

magnetic field

Answer 1

a region where certain metals experience a force

Question 2

types of metals that are attracted to magnets

Answer 2

SINC ((mild)steel, iron, nickel, cobalt), (not stainless steel)

Question 3

what is the magnetic field represented by?

Answer 3

lines and arrows pointing from the north to south

Question 4

what is a compass?

Answer 4

a small bar magnet

Question 5

what is the earth made out of? is it magnetic?

Answer 5

iron; yes

Question 6

is the geographic north pole the same as the magnetic north pole?

Answer 6

no; the geographic north pole is actually the magnetic south pole since a compass points to the north at the geographic north pole and is attracted to the magnetic south pole

Question 7

domains

Answer 7

tiny patches of magnetism like a small magnet with north and south pole

Question 8

how to make an iron rod magnetic?

Answer 8

stroke it with a magnet which pulls the originally randomly organised domains into line

Question 9

can i make copper or aluminum magnetic?

Answer 9

no, because they are non-magnetic; and in non-magnetic metals, there are no domains to be lined up

Question 10

how can i see magnetic fields between two magnets?

Answer 10

put plastic sheet over magnets and pour iron filings onto the sheet

Question 11

what kinds of metals can become an electromagnet and how?

Answer 11

any kinds of metal, as long as you pass current through it, it will become and electromagnet

Question 12

how to make the electromagnetic field stronger?

Answer 12

• use more current
• coil up the wire (straight wire: right-hand grip rule circular magnetic field, coiled wire: resembled the magnetic field of bar magnet)
• insert a SINC core (e.g. iron nail) (it can amplify the magnetic field as it aligns with the wire’s)

Question 13

what is a relay and why do we need it? example

Answer 13

a type of electromagnetic switch
used when we want a low current circuit to turn on a high current circuit
e.g. in the car ignition system so the driver doesn’t come in direct contact with the high current circuit

Question 14

process of relay

Answer 14

1. switch is pushed
2. first circuit is completed
3. current flows through the first circuit
4. the electromagnet is activated by the current in the first circuit
5. the electromagnet attracts the iron arm
6. the iron arm rotates
7. the iron arm completes the second circuit
8. current flows through the second circuit
   (e.g. 9. the motor is switched on)

Question 15

right hand grip rule

Answer 15

thumb points up (direction of current)
fingers curl around (direction of magnetic field lines)

Question 16

dart method

Answer 16

if the symbol is a dot, that means the dart is facing you and the current is flowing towards you so point your right thumb to yourself and check the direction of the current
if the symbol is a cross, that means the dart is facing away from you and the current is flowing away you so point your right thumb away and check the direction of the current

Question 17

solenoid

Answer 17

coil that can act as an electromagnet