PHYSICS TOPIC 7

Question 1

A magnetic compass is

Answer 1

a tiny needle pivoted at its centre.

Question 2

compasses show

Answer 2

directions of magnetic fields.

Question 3

magnets can be

Answer 3

permanent or induced

Question 4

permanent magnets

Answer 4

produce their own magnetic field

Question 5

induced magnets are

Answer 5

magnetic materials that turn into a magnet when they’re put into a magnetic field.

Question 6

the closer the field lines

Answer 6

the stronger the magnetic field.

Question 7

magnetic field is strongest at

Answer 7

the poles of a magnet

Question 8

the force between permanent and induced magnets is always

Answer 8

attractive.

Question 9

a solenoid is a

Answer 9

coil of wire.

Question 10

solenoids

Answer 10

increase the strength of the magnetic field.

Question 11

the magnetic field inside a solenoid is

Answer 11

strong and uniform

Question 12

how to increase field strength of solenoid

Answer 12

• putting block of pure/soft iron in centre of coil
• the iron core becomes an induced magnet

Question 13

the larger the current through the wire or the closer to the wire you are

Answer 13

• the stronger the magnetic field is.

Question 14

a moving charge creates a

Answer 14

magnetic field

Question 15

a solenoid with an iron core is called an

Answer 15

ELECTROMAGNET

Question 16

size of force =

Answer 16

F = BIL

Question 17

force acting on a conductor in a magnetic field depends on…. x3

Answer 17

• the magnetic flux density
• size of current through the conductor
• length of conductor that’s in the magnetic field

Question 18

4 ways to increase electromagnetic strength

Answer 18

• increase current
• increase number of turns in solenoid
• decrease length but keep number of coils the same.
• add iron core

Question 19

motor effect

Answer 19

• when a wire carrying a current is put between magnetic poles, the magnetic field around the wire interacts with the magnetic field between the poles, causing them to exert a force on each other.

Question 20

to experience full force

Answer 20

the wire has to be 90 degrees to the magnetic field.

Question 21

3 ways to increase speed of motor

Answer 21

• increase current
• add more turns to coil
• increase magnetic flux density by using more powerful magnets.

Question 22

a split ring communicator

Answer 22

• swaps the positive and negative connections every half turn
• so the direction of the current swaps every half turn
• meaning forces acting on coil will always be acting in the same direction.