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physics > magnetism and electromagnetism > Flashcards

magnetism and electromagnetism Flashcards

1
Q

at which part of a magnet are the magnetic forces stronger

A

the poles of the magnet

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2
Q

what happens when two magnets are brought close to each other

A

the exert a force on each other

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3
Q

what type of force is exerted if two like poles of a magnet are brought near each other

A

a repulsive
non-contact force

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4
Q

what type of force is exerted if two unlike poles of a magnet are brought near each other

A

an attractive
non-contact force

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5
Q

what is the difference between a permanent magnet and an induced magnet

A

a permanent magnet produces its own magnetic field
an induced magnet becomes magnetic when placed in a magnetic field

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6
Q

what type of force does induced magnetism always cause

A

a force of attraction

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7
Q

what happens when an induced magnet is removed from a magnetic field

A

the induced magnet loses most/all of its magnetism

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8
Q

what is a magnetic field

A

the region surrounding a magnet where another magnet or magnetic material experiences a non-contact force

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9
Q

give 4 examples of magnetic materials

A
  1. iron
  2. steel
  3. cobalt
  4. nickle
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10
Q

what can always be said about the force between a magnet and magnetic materials

A

it is always attractive

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11
Q

how does the stength of a magnetic field alter as you move further away from the magnet producing it

A

the magnetic field strength decreases the further you move away

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12
Q

in which direction does a magnetic field point

A

in the direction that a North Pole would experience a force is placed in the field
from the north seeking pole to the south seeking pole of a magnet

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13
Q

what does a magnet compass contain

A

a small bar magnet that points in the direction of the earths magnetic field

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14
Q

what is produced when current flows through a conducting wire

A

a magnetic field is produced around the wire

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15
Q

what determines the strength of the magnetic field around a current carrying wire

A

the magnitude of the current flowing through the wire
the distance from the wire

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16
Q

what is a solenoid

A

a coil of wire which when current passes through creates a strong magnetic field

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17
Q

describe the magnetic field found inside a solenoid

A

strong and uniform

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18
Q

what is an electromagnet

A

a solenoid with an added iron core
adding the iron core increase the strength of the magnetic field

19
Q

what is the motor effect

A

when a force is exerted between a magnetic field and a current carrying conductor placed in that field

20
Q

what rule is used to determine the force experiences due to the motor effect

A

flemings left-hand rule

21
Q

when using flemings left hand rule what does the forefinger represent

A

the forefinger points in the direction of the magnetic field

22
Q

when using flemings land hand rule what does the second finger represent

A

the 2nd finger points in the direction of current flow in the conductor

23
Q

what factors affect the size of the force on a current-carrying wire in a magnetic field

A

the magnitude of the current flowing through a conductor
the strength of the magnetic field that the conductor is placed in

24
Q

if the direction of current in a current carrying wire is placed in a uniform magnetic field is reversed, what happens to the force

A

the direction of the force is reversed

25
Q

if the strength of the current in a current carrying wire placed in a uniform magnetic field is increased, what happens to the force?

A

the strength of the force is increased

26
Q

what criteria must be met for the equation linking force, magnetic flux density, current and length to hold

A

the conductor must be at right-angles to the magnetic field it is placed in

27
Q

what is the unit for magnetic flux density

A

Tesla T

28
Q

how does an electric motor work

A

a coil of wire, carrying a current, is placed in a magnetic field
the forces on the two sides perpendicular to the field experience forces in opposite directions
this causes a rotational effect

29
Q

how do loudspeakers make use of the motor effect

A

the motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound

30
Q

explain how a loudspeaker works

A

a cone with a wire wrapped around it is connected to an a.c power supply and is placed in a permanent magnetic field
when current flows through the wire, it creates a second magnetic field, which interacts with the permanent field
this produces a force which causes the cone to vibrate

31
Q

how is the pitch of the sound form a loudspeaker changed

A

the frequency of the a.c current is altered
this creates a different frequency of vibration in the cone

32
Q

what happens when an electrical conductor moves relative to a magnetic field

A

a potential difference is induced across the ends of the conductor

33
Q

what happens to an electrical conductor when there is a change to the magnetic field that is placed in?

A

a potential difference is induced across the ends of the conductor

34
Q

what is the requirement for an induced potential difference to cause a current flow

A

the conductor must form a closed loop or be part of a complete circuit

35
Q

what can be said about the direction of the magnetic field produced by an induced current

A

the direction of the field is such that it imposes the change that induced the current
this change is either the movement of the conductor or a change to the field

36
Q

what are 2 ways that the generator effect is used to generate different types of current

A

in an alternating to produce alternating current
in a dynamo to produce direction current

37
Q

what electromagnetic effect does a microphone take advantage of and how

A

the generator effect
it converts the pressure variations in sound waves into alternating current in a circuit

38
Q

describe the makeup of a basic transformer
huh

A

a primary coil and a secondary coil of wire wrapped around a iron core

39
Q

why is iron used as the core for a transformer

A

it is easily magnetised

40
Q

explain how a transformer works

A

an alternating current flows through the primary coil
this induces a changing magnetic field in the core
this changing magnetic induces a current to flow in the secondary coil

41
Q

why must the current flowing through the primary coil of a transformer be alternating?

A

for current to be induced in the secondary coil, the magnetic field in the core must be continuously changing
for the magnetic field to be changing, the current in the primary coil must be alternating

42
Q

what can be said about the electrical power put and output of a 100% efficient transformer?

A

the electrical power input is equal to the electrical power output

43
Q
A

physics (9 decks)

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