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Pro Physics > P15 > Flashcards

P15 Flashcards

1
Q

What is an example of a non-contact force?

A

Attraction and repulsion between two magnetic poles

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2
Q

What are the two types of magnets?

A

Permenant or induced

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3
Q

What are permenant magnets?

A

Produce their own magnetic field

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4
Q

What are induced magnets?

A

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

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5
Q

What are some examples of magnetic materials?

A

Iron,steel,nickel,cobalt

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6
Q

What is the force between induced and permenant magnets?

A

Attractive

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7
Q

What happens when induced take away magnetic field?

A

Lose magnetism

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8
Q

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

A

Exert a force on each other

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9
Q

What happens when two poles are the same?

A

They repel each other

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10
Q

What happens to two unlike poles?

A

They attract each other

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11
Q

Whats the magnetic field?

A

A region where other magnets or magnetic materials experience a force

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12
Q

What does the strength of the magnetic field depend on?

A

The distance from the magnet (strongest at the poles)

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13
Q

How is the direction of the magnetic field given?

A

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

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14
Q

What doees a magnetic field contain?

A

A bar magnet

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15
Q

How does a compass work?

A

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

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16
Q

What happens when a current flows through the wire?

A

A magnetic field is created around the wire

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17
Q

What does the strength of the magnetic field depend on?

A
  • Current of wire and distance
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18
Q

How can you increase the strength of a magnetic field?

A

Wrap the wire in Solenoid

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19
Q

How is the magnetic field in the solenoid?

A

Strong and uniform

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20
Q

How can solenoid increase magnetic field?

A

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

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21
Q

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

A

Put a block of iron in the centre of the coil

22
Q

How are electromagnets used in cranes?

A

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.

23
Q

What is the motor effect?

A

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

24
Q

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

A
  • Magnetic flux density
  • the size of the current
  • the length of the conductor
25
Q

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

A

F = BI1

26
Q

What is B in BI1?

A

Flux density (tesla)

27
Q

What is I in BI1?

A

Current (amps)

28
Q

What is 1 in BI1?

A

Length (meter)

29
Q

Explain the electric motor in breif terms?

A

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

30
Q

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

A

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

31
Q

What do loudspeakers and headphones use?

A

Electromagnets

32
Q

Why do loudspeakers and headphones use the motor effect?

A

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

33
Q

How do moving coil loudspeakers work?

A

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

34
Q

What is the generator effect?

A

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

35
Q

What is an induced current?

A

Opposes the change that made it

36
Q

What factors affect the size of induced potential difference?

A

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

37
Q

Give an example of the generator effect?

A

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

38
Q

What do alternaters do?

A

Generate alternating current.

39
Q

Explain how generator effect is used in alternator?

A

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

40
Q

What do dynamos produce?

A

Direct current

41
Q

How do dynamos generate current?

A

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

42
Q

How is ac shown on a graph?

A

Up and down

43
Q

How is dc shown in a graph?

A

Above axis

44
Q

How is increasing revolutions shown?

A

Up and down. Lots of peaks

45
Q

How do microphones use the generator effect?

A

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

46
Q

How does a moving coil microphone work?

A

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

47
Q

What is a transformer?

A

Changes the size of the potential difference of an alternating current

48
Q

What do transformers only work with?

A

Alternating currents

49
Q

What does a basic transformer consist of?

A

A primary coil and a secondary wound on iron core

50
Q

What is the potential differencecalculation?

A

Vp / Vs = Np / Ns

51
Q

What are the ratios between primary and secondary?

A

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

Pro Physics (14 decks)

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