Mangets Flashcards
1
Q
What is a magnetic field?
A
A region around a magnet in which the influence of the magnet can be felt or detected.
2
Q
What is the direction of a magnetic field?
A
The direction in which a N-pole placed at that point will tend to move.
3
Q
What are magnetic lines of force?
A
Imaginary lines along which a free-North pole would tend to move if placed in the field.
4
Q
How can magnetic field patterns be observed?
A
Using iron filings.
5
Q
What is the pattern of the magnetic field around a straight conductor carrying current?
A
Concentric circles with the wire as the center.
6
Q
How is the direction of the magnetic field around a current-carrying wire determined?
A
By applying the Right Hand Grip rule or Clenched Fist rule.
7
Q
What is a solenoid?
A
A long cylindrical coil of wire whose turns are usually wound close together.
8
Q
What is the pattern of the magnetic field around a solenoid?
A
Similar to that around a bar magnet
9
Q
What are magnetic substances?
A
Substances that can attract or be attracted by even weak magnets.
10
Q
Examples of magnetic substances
A
Iron
11
Q
What are non-magnetic substances?
A
Substances that are not attracted by magnets and have feeble magnetic properties.
12
Q
Examples of non-magnetic substances
A
Copper
13
Q
What are temporary magnets?
A
Magnets made from soft-iron that lose their magnetic properties easily.
14
Q
What are permanent magnets?
A
Magnets made from steel that do not lose their magnetism easily.
15
Q
How are magnets made using the electrical method?
A
By inserting the material to be magnetized inside a solenoid and passing a current through the solenoid.
16
Q
How is the polarity of an electromagnet determined?
A
The polarity depends on the direction of current flow in the solenoid. Anticlockwise current flow produces a North pole
17
Q
Describe the single touch method of making a magnet.
A
Stroking a specimen with one end of a bar magnet in the same direction repeatedly.
18
Q
Describe the double touch method of making a magnet.
A
Stroking each half of the specimen repeatedly in opposite directions with opposite poles of two bar magnets
19
Q
What is demagnetization?
A
The process of making a magnet lose its magnetism.
20
Q
How can demagnetization be achieved?
A
Electrical method (using alternating current)
21
Q
What is the probable cause of the earth’s magnetic field?
A
Large electric currents circulating in the earth’s core.
22
Q
Where are the earth’s magnetic poles located?
A
Near the geographical north and south poles but not exactly at the poles.
23
Q
What is the angle of dip (or inclination)?
A
The angle which the earth’s magnetic field makes to the horizontal at any particular place.
24
Q
What is the declination at a place?
A
The angle between the true geographical north and the magnetic north at that place.
25
What is a magnetic meridian?
An imaginary vertical plane passing through the earth's magnetic axis.
26
What is a horizontal component of the earth's magnetic field?
The component of the earth's magnetic field in the horizontal direction.
27
What is the relationship between the angle of dip and the horizontal component at the magnetic poles?
At the magnetic poles
28
What are isoclinic lines?
Imaginary lines drawn on a map joining places with the same angle of dip.
29
What are isogonic lines?
Imaginary lines drawn on a map joining places with the same magnetic declination.
30
What is the relationship between magnetic force
charge
31
What is the unit of magnetic flux density (B)?
Tesla (T).
32
What is the cross product of two vectors V and B?
V x B = VB sin θ
33
When is the magnetic force on a moving charge zero?
When V and B are in the same direction (θ = 0°)
34
Front
Back
35
What is an electromagnetic field?
"A field representing the joint interaction of electric and magnetic forces."
36
What two types of forces give rise to an electromagnetic field?
"Electric and magnetic forces."
37
True or False: An electromagnetic field is considered to have its own objective existence in space.
"True"
38
What happens when an electromagnetic field exerts force on charged particles?
"The charged particles move."
39
What is the equation for the force on a charge q moving with velocity v in an electromagnetic field?
"F = q(E + v x B)"
40
What is always accompanied by a changing electric field?
"A magnetic field."
41
What is always accompanied by a changing magnetic field?
"An electric field."
42
What kind of field is produced by a current-carrying wire?
"A magnetic field
43
What happens to a conductor carrying electric current when placed in a magnetic field?
"It experiences a mechanical force."
44
Front
Back
45
What happens to a current-carrying conductor placed in a magnetic field?
"It experiences a mechanical force."
46
Describe the demonstration setup used to show the force on a current-carrying conductor in a magnetic field.
"A copper rod is placed across two metal rails fixed on each side of a horseshoe magnet."
47
What happens to the copper rod when current is passed through it in the magnetic field?
"It rolls along the rails."
48
How does increasing the current affect the force on the rod?
"The force increases
49
What happens when the direction of current flow is reversed?
"The rod moves in the opposite direction."
50
What happens to the force on the rod if the magnetic field is parallel to its length?
"There is no force on the rod
51
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52
Does a magnetic field exert a force on a moving charge?
"Yes"
53
What constitutes an electric current?
"Charges in motion"
54
Give examples of charges in motion that constitute an electric current.
"Motion of electrons in wires
55
What vector quantity represents the strength of a magnetic field?
"B
56
What is the unit of flux density (B)?
"Tesla (T) or Weber per square meter (Wb/m^2)"
57
What is the formula for the force (F) on a charge (q) moving with velocity (V) in a magnetic field (B)?
"F = qVB sin(theta)
58
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Back
59
In the formula F = qVB sin(theta), what do the variables represent?
"F = force
60
What is another way to represent V x B?
"VB sin(theta)"
61
What does V x B represent?
"The cross product of vectors V and B"
62
What is the value of the force (F) when V and B are in the same direction?
"Zero"
63
Why is the force zero when V and B are in the same direction?
"Because the angle theta is zero
64
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Back
65
What fields were studied as independent in previous chapters?
"Electric field and magnetic field"
66
What does this chapter discuss?
"The field representing the interaction of electric and magnetic forces (electromagnetic field)"
67
What is an electromagnetic field?
"A field representing the joint interaction of electric and magnetic forces"
68
Does an electromagnetic field have its own objective existence in space?
"Yes
69
What does an electromagnetic field exert forces on?
"Charged particles"
70
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71
What is observed when a conductor carrying an electric current is placed in a magnetic field?
"It experiences a mechanical force."
72
How is this demonstrated in the experiment?
"Using metal rails
73
What happens to the copper rod when current flows through it in the magnetic field?
"It rolls along the rails."
74
What happens to the force on the rod when the current is increased?
"The force increases."
75
What happens to the direction of the force when the direction of the current is reversed?
"The direction of the force reverses."
76
What is the force on the rod if the magnetic field is parallel to the rod's length?
"The force is zero."
77
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78
What does the observation of a current-carrying wire having a magnetic field around it indicate?
"That the magnetic field is directly related to the moving electricity (current) in the wire."
79
What is the general relationship between changing electric and magnetic fields?
"A changing electric field is always accompanied by a magnetic field
80
What term describes the interaction or interplay of electric and magnetic forces?
"Electromagnetic field"
81
What is the formula that gives the force on a charge q moving with a velocity v in an electromagnetic field?
"F = q(E + v x B)"
82
In the formula F = q(E + v x B), what do E and B represent?
"E = electric field
83
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84
What does the term 'v x B' represent in the force equation F = q(E + v x B)?
"The cross product of the velocity (v) and magnetic field (B) vectors"
85
What does the cross product 'v x B' determine?
"The direction of the magnetic force on the moving charge"
86
In what direction is the magnetic force always oriented?
"Perpendicular to both the velocity of the charge and the magnetic field direction"
87
What happens to the electric field when there is a changing magnetic field?
"A changing magnetic field induces an electric field"
88
What happens to the magnetic field when there is a changing electric field?
"A changing electric field induces a magnetic field"
89
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90
What does the direction of the force on a current-carrying conductor in a magnetic field depend on?
"Both the direction of the current and the direction of the magnetic field"
91
How is the relationship between current, magnetic field, and force demonstrated?
"With a setup using a horseshoe magnet
92
If the current through the conductor is increased, what happens to the force on the conductor?
"The force increases proportionally"
93
If the direction of the magnetic field is reversed, what happens to the direction of the force on the conductor?
"The direction of the force is reversed"
94
Under what condition is there no force on a current-carrying conductor in a magnetic field?
"When the conductor is oriented such that the current is parallel to the magnetic field"
95
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Back
96
What does the experiment with the copper rod on rails demonstrate?
"That a magnetic field exerts a force on a current-carrying conductor"
97
How does the strength of the magnetic field affect the force on the conductor?
"A stronger magnetic field will exert a greater force (this is implied in the text
98
What is the relationship between the direction of the force and the orientation of the conductor relative to the magnetic field?
"The force is maximum when the conductor is perpendicular to the field and zero when it's parallel"
99
What rule can be used to determine the direction of the force on a current-carrying conductor in a magnetic field?
"Fleming's Left-Hand Rule (This rule is implied in the concepts
100
What are some practical applications of the force on a current-carrying conductor in a magnetic field?
"Electric motors
101
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102
What are the key factors that determine the magnitude of the force on a current-carrying conductor in a magnetic field?
"The strength of the magnetic field
103
When is the force on a current-carrying conductor in a magnetic field maximized?
"When the conductor is perpendicular to the magnetic field lines"
104
When is the force on a current-carrying conductor in a magnetic field minimized (zero)?
"When the conductor is parallel to the magnetic field lines"
105
In the demonstration with the copper rod and rails, what happens when the direction of the current is reversed?
"The direction of the rod's motion is reversed"
106
Does the material of the conductor affect the force experienced in a magnetic field?
"Not explicitly mentioned in this section
107
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108
What is the general principle behind the force on a current-carrying conductor in a magnetic field?
"The magnetic field exerts a force on the moving charges (current) within the conductor."
109
In the copper rod and rails experiment, what does the rod's movement indicate?
"That the magnetic force is doing work on the rod."
110
How is the magnitude of the force related to the number of charge carriers in the conductor?
"More charge carriers (higher current) result in a greater force."
111
How does the length of the conductor within the magnetic field affect the force?
"A longer conductor experiences a greater force (this is implied
112
Is the force on a current-carrying conductor a vector or scalar quantity?
"Vector quantity (it has both magnitude and direction)"
113
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114
What is the relationship between the direction of the magnetic force on a current-carrying conductor and the direction of the electron flow?
"The force is perpendicular to the direction of electron flow (which is opposite to conventional current)."
115
In the experiment with the magnet, rails, and rod, what happens if you increase the strength of the magnet?
"The force on the rod increases
116
Does the formula F = q(E + v x B) apply to the force on a current-carrying wire?
"Yes
117
What is the overall effect of the magnetic force on the electrons within the current-carrying conductor?
"It results in a macroscopic force on the conductor itself."
118
How does this force relate to the working principle of an electric motor?
"The force on current-carrying wires in a magnetic field is what causes the motor to rotate."
119
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120
What is the significance of the 'left-hand rule' in the context of a current-carrying conductor in a magnetic field?
"It's a mnemonic to help determine the direction of the force
121
In the experiment with the rod and rails, what happens if the horseshoe magnet is replaced with a weaker magnet?
"The force on the rod decreases
122
Does the force on a current-carrying conductor in a magnetic field do work?
"Yes
123
How does the concept of energy conservation relate to the movement of the conductor in the magnetic field?
"The electrical energy supplied to the conductor is converted into kinetic energy of the conductor's motion."
124
What are some real-world devices that utilize the principle of force on a current-carrying conductor in a magnetic field?
"Electric motors
125
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126
What happens to the magnetic field created by the current in the conductor when an external magnetic field is applied?
"The external magnetic field exerts a force on the conductor due to its own magnetic field."
127
How does the angle between the conductor and the magnetic field affect the magnitude of the force?
"The force is proportional to the sine of the angle between them."
128
In the experiment with the copper rod, what role does the rheostat play?
"It controls the amount of current flowing through the rod."
129
What is the relationship between the direction of the force and the polarity of the magnet?
"Reversing the polarity of the magnet reverses the direction of the force."
130
Can a magnetic field do work on a stationary charge?
"No
