Magnetism Flashcards
1
Q
What are the two poles of a magnet called?
A
North and South
2
Q
What does the Law of Magnetism state about like poles?
A
Two like poles repel each other
3
Q
What does the Law of Magnetism state about unlike poles?
A
Two unlike poles attract each other
4
Q
What is a magnetic material?
A
Material attracted to a magnet
5
Q
Name three metals that are magnetic.
A
- Iron
- Cobalt
- Nickel
6
Q
What happens to a magnetic material when it is placed in a magnetic field?
A
It can be turned into a magnet temporarily
7
Q
What is induced magnetism?
A
Temporary magnetism in a material placed in a magnetic field
8
Q
What is the behavior of magnetic materials when brought near a magnet?
A
They will always be attracted to the magnet
9
Q
What is a permanent magnet?
A
A magnet made of permanent magnetic materials that does not lose its magnetism
10
Q
What is the definition of a magnetic field?
A
The region around a magnet where a force acts on another magnet or magnetic material
11
Q
How are magnetic field lines represented?
A
Using arrows to show direction and spacing to show strength
12
Q
What does close spacing of magnetic field lines indicate?
A
A strong magnetic field
13
Q
What does far spacing of magnetic field lines indicate?
A
A weak magnetic field
14
Q
From which pole to which pole do magnetic field lines go?
A
From north to south
15
Q
In a uniform magnetic field, how is the strength and direction represented?
A
Equal spacing between lines and arrows pointing in the same direction
16
Q
True or False: A uniform magnetic field is created when two opposite poles are held close together.
A
True
17
Q
What is the shape of a magnetic field around a bar magnet?
A
It is strongest at the poles and weakens with distance
18
Q
What happens to a magnetic compass in the absence of any magnet?
A
It will always point north
19
Q
The north pole of a magnetic compass is attracted to which pole of the Earth?
A
Earth’s magnetic south pole
20
Q
Fill in the blank: The north pole of the Earth acts like the _______ of a magnet.
A
South pole
21
Q
What is the significance of the Earth’s magnetic field?
A
It indicates that the core of the Earth is magnetic
22
Q
What is the relationship between geographic and magnetic poles of the Earth?
A
The geographic North Pole is a magnetic south pole
23
Q
What is produced around a conducting wire when a current flows through it?
A
A magnetic field
A conducting wire is any wire that has current flowing through it.
24
Q
How can the shape and direction of the magnetic field around a wire be investigated?
A
Using plotting compasses
25
What pattern do magnetic field lines around a current-carrying wire form?
Concentric circles
26
What does a circular field pattern around a wire indicate?
The magnetic field has no poles
27
What happens to the strength of the magnetic field as the distance from the wire increases?
It gets weaker
28
What rule is used to determine the direction of the magnetic field around a wire?
Right-hand thumb rule
29
What happens to the magnetic field if there is no current flowing through the conductor?
There will be no magnetic field
30
What effect does increasing the amount of current have on the magnetic field strength around a wire?
It increases the strength of the magnetic field
31
What is the magnetic field around a solenoid compared to?
A bar magnet
32
What defines the polarity of a solenoid?
The direction of the current flow
33
If the current in a solenoid is traveling clockwise, what pole does it represent?
South pole
34
How can the strength of the magnetic field around a solenoid be increased?
By:
* Increasing the current
* Increasing the number of turns in the coil
* Reducing the length of the wire
* Adding an iron core
35
What is an electromagnet?
A solenoid with an iron core
36
What happens to the magnetic field produced by an electromagnet when the current is switched off?
There will be no magnetic field
37
What are two examples of devices that use electromagnets?
* Scrapyard crane
* Electric bell
38
What occurs when the button is pressed on an electric bell?
Current passes through the electromagnet creating a magnetic field
39
What is the motor effect?
When a wire with current in a magnetic field experiences a force
40
What two magnetic fields interact in the motor effect?
* Magnetic field around the wire
* External magnetic field
41
What factors can increase the size of the force exerted by magnetic fields?
By:
* Increasing the current
* Using stronger magnets
* Placing the wire at 90° to the magnetic field
42
What is the equation used to calculate the force acting on a current-carrying wire in a magnetic field?
F = BIL
43
What does 'F' represent in the equation F = BIL?
Force acting on the current-carrying wire in Newtons (N)
44
What is Fleming's Left-Hand Rule used for?
To determine the direction of force, magnetic field, and current
45
What should the thumb, first finger, and second finger represent in Fleming's Left-Hand Rule?
* Thumb: Direction of the force
* First Finger: Direction of the magnetic field
* Second Finger: Direction of the current
46
What is a simple d.c. electric motor based on?
The motor effect
47
What causes the coil in a d.c. motor to rotate?
Forces acting in opposite directions on each side of the coil
48
What happens when the coil in a d.c. motor reaches the vertical position?
No force acts on the coil as the split ring is not in contact with the brushes
49
How can the speed of rotation in a d.c. motor be increased?
By:
* Increasing the current
* Using a stronger magnet
50
What happens to the direction of rotation if the direction of current supply is reversed?
The direction of rotation of the coil changes
51
What is one way to increase the force supplied by a d.c. motor?
Increasing the strength of the magnetic field
52
What is the first step to determine the direction of rotation in a motor?
Draw arrows to show the direction of the magnetic field lines
## Footnote
The magnetic field lines go from the north pole of the magnet to the south pole of the magnet.
53
What is the direction of current flow in the coils of a motor?
From the positive terminal of the battery to the negative terminal
## Footnote
This is crucial for understanding how the motor operates.
54
What does Fleming’s left hand rule help determine?
The direction of the force on each side of the coil
## Footnote
It uses the orientation of the fingers to establish the relationship between the magnetic field, current, and force.
55
In Fleming's left hand rule, what does the First Finger represent?
The direction of the magnetic Field
## Footnote
This is the starting point for using the rule.
56
In Fleming's left hand rule, what does the seCond Finger represent?
The direction of the Current
## Footnote
This indicates the flow of electrical current through the coil.
57
In Fleming's left hand rule, what does the THumb represent?
The direction of the THrust (the force)
## Footnote
This indicates the force acting on the coil due to the interaction of the magnetic field and current.
58
What will the coil's direction of rotation be if the force arrows indicate opposite directions?
Clockwise
## Footnote
The opposing forces on each side of the coil create rotation.
59
What is the primary function of loudspeakers and headphones?
Convert electrical signals into sound
## Footnote
This process utilizes the motor effect.
60
What does a loudspeaker consist of?
A coil of wire wrapped around one pole of a permanent magnet
## Footnote
This structure is essential for generating sound.
61
What type of current passes through the coil of a loudspeaker?
Alternating current
## Footnote
This is crucial for creating a changing magnetic field.
62
What happens to the magnetic field around the coil when alternating current flows?
It creates a changing magnetic field
## Footnote
The direction of the field changes as the current changes direction.
63
What is the effect of the changing magnetic field on the coil in a loudspeaker?
It exerts a force on the coil
## Footnote
This force causes the coil to oscillate.
64
What is the result of the oscillating coil in a loudspeaker?
The speaker cone oscillates, creating sound waves
## Footnote
This is how sound is produced from electrical signals.
65
True or False: Loudspeakers and microphones perform the same function.
False
## Footnote
They look similar but have very different functions.
66
What type of current is used in a d.c. motor?
Direct current
## Footnote
This is different from the alternating current used in loudspeakers.
67
Fill in the blank: The explanation of how a loudspeaker works is similar to that of a _______.
motor
## Footnote
Both involve electromagnetic principles, but with different types of current.
68
What is the generator effect?
The generator effect is defined as: If an electrical conductor moves relative to a magnetic field or if there is a change in the magnetic field around a conductor, a potential difference is induced across the ends of the conductor.
69
What happens when a conductor moves through a magnetic field?
A potential difference is induced in the conductor as it cuts through the field lines.
70
List the factors that affect the induced potential difference.
* Speed at which the wire, coil, or magnet is moved
* Number of turns on the coils of wire
* Size of the coils
* Strength of the magnetic field
* Orientation of the poles of the magnet
71
True or False: Increasing the speed of the conductor increases the induced potential difference.
True
72
What is Lenz's Law?
Lenz's Law states that the direction of an induced potential difference always opposes the change that produces it.
73
What happens when a magnet is pushed into a coil of wire?
The end of the coil closest to the magnet will become a north pole, repelling the north pole of the magnet.
74
How does an alternator generate electricity?
An alternator converts energy from motion into an electrical output with an alternating current.
75
What components make up a simple alternator?
* Permanent magnet
* Rotating coil
* Slip rings
* Carbon brushes
76
What is the function of the slip rings in an alternator?
To allow the alternating current to flow between the coil and the external circuit.
77
Describe the output shape of an alternator's potential difference graph.
The output is a sine or cosine curve depending on the starting position of the coil.
78
What distinguishes a dynamo from an alternator?
A dynamo produces direct current (d.c.) while an alternator produces alternating current (a.c.).
79
What is the role of the split-ring commutator in a dynamo?
To change the connections between the coil and the external circuit every half turn.
80
Fill in the blank: A bicycle dynamo produces _______.
alternating current (a.c.)
81
What is the orientation of the coil when maximum induced potential difference occurs?
The coil is horizontal and moving perpendicular to the direction of the magnetic field.
82
When is no potential difference induced in the coil?
When the coil is vertical and moving parallel to the direction of the magnetic field.
83
What occurs when a magnet is pulled away from a coil of wire?
The end of the coil closest to the magnet will become a south pole, attracting the north pole of the magnet.
84
What type of current does a bicycle dynamo supply?
It supplies alternating current (a.c.) to bicycle lights.
85
Describe the graph of potential difference for a dynamo.
The graph is a sine curve and is always in the same direction.
86
What is the induced p.d. when the coil is at position 1 (starting point)?
The size of the induced p.d. is zero
## Footnote
Position 1 is where the coil is parallel to the magnetic field.
87
What happens to the induced p.d. when the coil has rotated by 90°?
The size of the induced p.d. is at a maximum
## Footnote
Position 2 is where the coil is horizontal and moving perpendicular to the magnetic field.
88
What is the induced p.d. when the coil has rotated by 180°?
The size of the induced p.d. is zero
## Footnote
Position 3 is where the coil is vertical and moving parallel to the magnetic field.
89
What happens to the induced p.d. when the coil has rotated by 270°?
The size of the induced p.d. is at a maximum and in the same direction as its position at 90° (position 2)
## Footnote
Position 4 is horizontal and moving perpendicular to the magnetic field.
90
What is the output potential difference when the coil completes a full 360° rotation?
The size of the induced p.d. is zero
## Footnote
The coil returns to its starting point, moving parallel to the magnetic field.
91
List the factors that can increase the magnitude of the induced p.d. in an alternator or dynamo.
* Increasing the frequency of rotation of the coil
* Increasing the number of turns on the coil
* Increasing the strength of the magnet
* Inserting a soft iron core into the coil
## Footnote
These factors enhance the electromagnetic induction process.
92
What is the function of a moving-coil microphone?
Microphones convert sound waves into electrical current
## Footnote
A moving-coil microphone operates based on the principles of the generator effect.
93
How does a moving coil microphone work?
Sound waves cause the diaphragm to vibrate, moving the coil through the magnetic field, which induces an alternating potential difference
## Footnote
The potential difference varies due to the diaphragm's vibrations.
94
True or False: Microphones and loudspeakers perform the same function.
False
## Footnote
They look similar but serve different purposes.
95
What is the primary purpose of a transformer?
To change the value of an alternating potential difference or current
## Footnote
This is achieved using the generator effect.
96
What are the main components of a basic transformer?
* A primary coil
* A secondary coil
* An iron core
## Footnote
Iron is used for its magnetic properties.
97
What occurs in the primary coil of a transformer?
An alternating current is supplied
## Footnote
This creates a changing magnetic field around the primary coil.
98
What does the changing magnetic field in the iron core produce?
A changing magnetic field inside the secondary coil
## Footnote
This induces a potential difference in the secondary coil.
99
The potential difference induced in a transformer will have the same frequency as what?
The alternating current supplied to the primary coil
## Footnote
This leads to an alternating current flow if the secondary coil is part of a circuit.
100
What is the transformer equation for potential differences?
Vp/Np = Vs/Ns
## Footnote
Where Vp and Vs are the potential differences across the primary and secondary coils, respectively, and Np and Ns are the number of turns on each coil.
101
What defines a step-up transformer?
Vs > Vp and Ns > Np
## Footnote
It increases the potential difference of a power source.
102
What defines a step-down transformer?
Vs < Vp and Ns < Np
## Footnote
It decreases the potential difference of a power source.
103
In a transformer, what does the term 'ideal transformer' refer to?
A transformer that is 100% efficient
## Footnote
It cannot increase power output due to the law of conservation of energy.
104
What is the equation for electrical power in a transformer?
P = V × I
## Footnote
Where P is power in Watts, V is potential difference in volts, and I is current in amps.
105
What role do transformers play in high voltage transmission?
* Increase potential difference before transmission
* Lower voltage for household use
* Adapt voltage for electronic devices
## Footnote
This reduces energy loss during transmission.
106
Why is electricity transmitted at high voltage?
To reduce the current and hence power loss in the cables
## Footnote
Higher voltage allows for a smaller current, reducing heating and energy loss.
