p4 - magnetism (from textbook)

Question 1

define magnetic field strength

Answer 1

the number of field lines passing through a particular area

Question 2

describe an induced magnet

Answer 2

an material in which all of its small magnetic regions (domains) are not lined up, but do line up in a magnetic field

Question 3

define a hard magnetic material

Answer 3

a substance that can be permanently magnetised and retains its magnetism after being magnetised

Question 4

define a soft magnetic material

Answer 4

a substance that can be easily magnetised and demagnetised, and is only temporarily magnetised

Question 5

why do compasses need to be wighted?

Answer 5

because of the earth’s dip - the angle between the field lines and a line horizontal to the surface of the earth

Question 6

what does a split ring commutator do?

Answer 6

swaps the positive and negative connections every half turn (aka the direction of the current)

Question 7

name 3 ways to increase the speed of electric motor rotations

Answer 7

-increase the current
-add more turns to the coil
-use stronger magnets
-increase length of the coile

Question 8

define electromagnetic induction

Answer 8

an induced potential difference is produced across the ends of a wire if the wire is in a changing magnetic field so that it cuts field lines, or flux lines

Question 9

how do you increase the induced potential difference in electromagnetic induction?

Answer 9

-moving the wire faster
-using a stronger magnetic field
-increasing the number of coils

Question 10

how do you increase the output in an alternator and a dynamo?

Answer 10

-use a stronger magnetic field
-use more turns on the coil
-spin the coil faster