P15

Question 1

What is an example of a non-contact force?

Answer 1

Attraction and repulsion between two magnetic poles

Question 2

What are the two types of magnets?

Answer 2

Permenant or induced

Question 3

What are permenant magnets?

Answer 3

Produce their own magnetic field

Question 4

What are induced magnets?

Answer 4

Magnetic materials that turn into a magnet when put in a magnetic field

Question 5

What are some examples of magnetic materials?

Answer 5

Iron,steel,nickel,cobalt

Question 6

What is the force between induced and permenant magnets?

Answer 6

Attractive

Question 7

What happens when induced take away magnetic field?

Answer 7

Lose magnetism

Question 8

What happens when you put two magnets of pole near each other?

Answer 8

Exert a force on each other

Question 9

What happens when two poles are the same?

Answer 9

They repel each other

Question 10

What happens to two unlike poles?

Answer 10

They attract each other

Question 11

Whats the magnetic field?

Answer 11

A region where other magnets or magnetic materials experience a force

Question 12

What does the strength of the magnetic field depend on?

Answer 12

The distance from the magnet (strongest at the poles)

Question 13

How is the direction of the magnetic field given?

Answer 13

Direction of the force that would act on another north pole.

Question 14

What doees a magnetic field contain?

Answer 14

A bar magnet

Question 15

How does a compass work?

Answer 15

Earth has a magnetic field and the compass points to the magnetic field

Question 16

What happens when a current flows through the wire?

Answer 16

A magnetic field is created around the wire

Question 17

What does the strength of the magnetic field depend on?

Answer 17

• Current of wire and distance

Question 18

How can you increase the strength of a magnetic field?

Answer 18

Wrap the wire in Solenoid

Question 19

How is the magnetic field in the solenoid?

Answer 19

Strong and uniform

Question 20

How can solenoid increase magnetic field?

Answer 20

The field lines around each loop line up with each other. Closer the feild lines stronger they are

Question 21

How can you increase the feild strength of a solenoid even more?

Answer 21

Put a block of iron in the centre of the coil

Question 22

How are electromagnets used in cranes?

Answer 22

Used to attract and pick up thing made from magnetic materials. Switch is turned on to pick up things and switched of to drop things.

Question 23

What is the motor effect?

Answer 23

When a current carrying wire is put between magnetic poles, the magnetic feild around the wire interacts with the magnetic field. This causes the magnet and conductor to exert force on each other

Question 24

What are the factors that affect the size of the force on the conductor?

Answer 24

• Magnetic flux density
• the size of the current
• the length of the conductor

Question 25

What is the equation when the current is 90° to the magnetic field?

Answer 25

F = BI1

Question 26

What is B in BI1?

Answer 26

Flux density (tesla)

Question 27

What is I in BI1?

Answer 27

Current (amps)

Question 28

What is 1 in BI1?

Answer 28

Length (meter)

Question 29

Explain the electric motor in breif terms?

Answer 29

A coill of wire carrying a current in a magnetic feild tends to rotate.

Question 30

How does the force in a conductor cause the rotation of a coil in a electric motor?

Answer 30

The coil is on a spindle and the forces act one up one down

Question 31

What do loudspeakers and headphones use?

Answer 31

Electromagnets

Question 32

Why do loudspeakers and headphones use the motor effect?

Answer 32

To convert variation in current in electrical circuts to pressure variation of sound waves

Question 33

How do moving coil loudspeakers work?

Answer 33

1) An alternating current is sent through coil of wire attatched to the base of the paper one. 2) the coil surrounds one pole so the current causes a force on the coil 3) when the current reverses the force acts in a opposite direction 4) variation in current make cone vibrate

Question 34

What is the generator effect?

Answer 34

The induction of potential difference in a wire which is moving relative to a magnetic field.

Question 35

What is an induced current?

Answer 35

Opposes the change that made it

Question 36

What factors affect the size of induced potential difference?

Answer 36

1) increasing speed of movement 2) increasing strength of magnetic field

Question 37

Give an example of the generator effect?

Answer 37

Moving a magnet in a coil wire or moving a conductor in a magnetic field

Question 38

What do alternaters do?

Answer 38

Generate alternating current.

Question 39

Explain how generator effect is used in alternator?

Answer 39

1) Alternator rotates the coil 2) As the coil spins a current is induced 3) acs have slip rings and brushes

Question 40

What do dynamos produce?

Answer 40

Direct current

Question 41

How do dynamos generate current?

Answer 41

1) Dynamos have split ring commutator instead of slip rings. This swaps the connection every half turn

Question 42

How is ac shown on a graph?

Answer 42

Up and down

Question 43

How is dc shown in a graph?

Answer 43

Above axis

Question 44

How is increasing revolutions shown?

Answer 44

Up and down. Lots of peaks

Question 45

How do microphones use the generator effect?

Answer 45

To convert pressure variations in sound waves in variations is current in electrical circuts

Question 46

How does a moving coil microphone work?

Answer 46

1) Sound waves hit a flexible diaphragm that is attatched to the coil. 2) Causes the coil to move in the magnetic field which generates a current

Question 47

What is a transformer?

Answer 47

Changes the size of the potential difference of an alternating current

Question 48

What do transformers only work with?

Answer 48

Alternating currents

Question 49

What does a basic transformer consist of?

Answer 49

A primary coil and a secondary wound on iron core

Question 50

What is the potential differencecalculation?

Answer 50

Vp / Vs = Np / Ns

Question 51

What are the ratios between primary and secondary?

Answer 51

Its the same between the number of turns on the primary and secondary