Magnetism

Question 1

define what a permanent magnet is

Answer 1

a magnet that produces it’s own magnetic field

Question 2

define what an induced magnet is

Answer 2

an object that becomes a magnet when it is placed in a magnetic field

Question 3

what is a magnetic field? (4)

Answer 3

• the area that a magnet affects is called a magnetic field
• the strength of the magnetic field depends on the distance from the magnet (weaker if the material is further away, stronger if it’s closer)
• it can be shown using iron filings or plotting compasses
• magnetic field lines never cross and have direction

Question 4

where is the strongest part of the magnetic field?

Answer 4

at the poles of the magnet

Question 5

why does the earth have a magnetic field?

Answer 5

because the core is made of iron and nickel

Question 6

what happens when a current flows through the wire in a circuit?

Answer 6

a magnetic field is produced around the wire

Question 7

if the polarity of the magnet or the flow of the current is reversed…

Answer 7

the wire swings in the opposite direction

Question 8

how do you make the magnetic field from a current stronger?

Answer 8

by shaping the wire into a solenoid

Question 9

how can the strength of an electromagnet be increased? (3)

Answer 9

by:

• increasing the current
• increasing the number of coils
• increasing the size of the iron core

Question 10

define electromagnet

Answer 10

a solenoid containing an iron core

Question 11

uses of electromagnets (4)

Answer 11

• maglev trains
• electronic looking doors (bank vault)
• door bells
• scrap yard crane

Question 12

fleming’s left hand rule

Answer 12

• when a wire carrying a current is placed in a magnetic field, the magnetic field and the wire exert a force on each other:

THUMB = motion
FIRST FINGER = field
SECOND FINGER = current