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IGCSE Physics > Chapter 4: Electricity and Magnetism {Pt 1} > Flashcards

Chapter 4: Electricity and Magnetism {Pt 1} Flashcards

1
Q

What is a magnet?

A

A material that produces a magnetic field

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2
Q

What are the ends of a magnet called?

A

poles

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3
Q

What are the two poles of the magnet?

A

The north pole and the south pole

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4
Q

Opposite poles of two magnets ____

A

attract

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5
Q

Like poles of two magnet___

A

repel from each other

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6
Q

Where is the magnetic field of a magnet the strongest at?

A

At its poles

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7
Q

What can magnetised materials do?

A

They can both repel and attract

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8
Q

What are magnetic materials?

A

Materials that will always be attracted to the magnet regardless of which pole is held close to it

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9
Q

Can unmagnetised materials be attracted to a magnet?

A

Yes, but they will never experience repulsion.

Only a magnet can repel another magnet

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10
Q

Why do magnets interact with each other?

A

Magnets exert forces and torques on each other due to the rules of electromagnetism.

The forces of attraction field of magnets are due to microscopic currents of electrically charged electrons.

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11
Q

Tell me about dipole interaction.

A

The most elementary force between magnets is the magnetic dipole.

If all of the magnetic dipoles that make up two magnets are known, then the net force on both magnets can be determined by summing up all these interactions between the dipoles of the first magnet and that of the second.

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12
Q

Why are the opposite poles of the magnet attracted to each other?

A

Magnets are drawn toward regions of higher magnetic field.
Every magnet produces a magnetic field that is stronger near its poles.
If opposite poles of two separate magnets are facing each other, each of the magnets are drawn into the stronger magnetic field near the pole of the other.

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13
Q

What is induced magnetism.

A

Magnetism acquired by a magnetic material when it is kept near a magnet.

Induced magnetism is temporary and it precedes attraction.

When a piece of un-magnetised magnetic material touches or is brought near to the pole of a permanent magnet, it becomes a magnet itself.

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14
Q

How are magnetic material classified?

A

Into hard (permanent) or soft materials (temporary)

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15
Q

What material is used for marking temporary magnets?

A

Soft iron.
It is highly susceptible but has a low retentivity, because of these properties, soft iron gets magnetised faster but loses its magnetism as soon as the inducing magnet is removed.
They are used in cranes to lift scrap metal.

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16
Q

What material is used for making permanent magnets?

A

Steel.
It has a low susceptibility but high retentivity.

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17
Q

Name some magnetic materials.

A

Iron
Steel
Cobalt
Nickel

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18
Q

What are magnetic materials?

A

Materials that are attracted to magnets and can be magnetised

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19
Q

What are non-magnetic materials?

A

Magnetic materials that are not attracted to magnets and cannot be magnetised.

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20
Q

Give examples of non-magnetic materials.

A

Glass
Plastic

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21
Q

Where are permanent magnets used in?

A

electric motors
magnetic recording and storage media
decorations

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22
Q

What type of magnets are electromagnets?

A

Temporary magnets

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23
Q

What is an electromagnet?

A

A magnet that works under the influence of applied electric current.

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24
Q

How is the strength of the magnetic field of the magnet altered?

A

By varying the power of the electric current.

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25
Q

How do you change the polarity of an electromagnet?

A

By altering the direction of the current.

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26
Q

What is the s.i unit of electric charge?

A

Coulomb (C)

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27
Q

What is electric field?

A

The electric force per unit charge

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28
Q

What is the direction of the electric field taken to be?

A

The direction of the force it would exert on a positive test charge

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29
Q

The electric field is ____________ from a positive change and ____________ a negative point charge.

A

radically outward
radically in toward

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30
Q

What happens is a charged object enters an electric field?

A

It experiences a force.

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31
Q

What type of quantity is electric field?

A

A vector quantity

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32
Q

How does a balloon get stuck on a wall?

A
  1. Rubbing of certain materials against one another produced electrostatic charges (transfer electrons)
  2. The balloon gains electrons
  3. The wall is more positively charged than the balloon.
  4. As the two come in contact, the balloon will stick to the wall.
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33
Q

What is charging?

A

The process of supplying the electric charge to an object or losing the electric charge from an object.

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34
Q

Draw the field lines of a positive and negative sphere

A
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35
Q

Draw the field lines of electrically charged parallel plates.

A
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36
Q

What are electrical conductors?

A

Electrical conductors conduct the electron current or flow of electrons fairly easily.

This is because they have delocalised electrons

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37
Q

Give an example of an electrical conductor.

A

Copper
Silver
Gold
Aluminium

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38
Q

What are electrical insulators?

A

Materials that don’t allow the flow of electrons.

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39
Q

Give some examples of insulators.

A

Glass
Plastic
Rubber
Air
Wood

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40
Q

What can be used to identify consductors?

A

A Gold-leaf electroscope.

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41
Q

Define electric current.

A

Rate of flow of electrons.

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42
Q

What is the s.i unit of electric current?

A

Ampere (A)

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43
Q

How is electric current measured?

A

Using an ammeter

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44
Q

Write the equation for calculating current.

A
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45
Q
A
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46
Q

How are ammeters connected in circuits?

A

In series.

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47
Q

How do the free electrons move across the circuit?

A

Electrons flow from the negative terminal through the conductor to the positive terminal.

They are repelled by the negative terminal and attracted by the positive terminal.

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48
Q

What is the direction of conventional current?

A

Positive terminal, through the conductor to the negative terminal

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49
Q

What is direct current?

A

Electricity always flows in a certain direction

50
Q

What is alternating current?

A

The positive and negative sides are constantly switched periodically and the direction of the flow of electricity changes accordingly

51
Q

What is electromotive force (e.m.f)>

A

The total word done by the electrical source in driving a unit charge around a complete circuit

52
Q

What is electromotive force measured in?

A

Volts

53
Q

Write the equation to calculate e.m.f.

A
54
Q
A
55
Q

What is potential difference?

A

The amount of energy given to electrons as they travel around a circuit.
Also known as voltage

56
Q

How can you measure voltage?

A

Using a voltmeter

57
Q

How is a voltmeter connected in a circuit?

A

In parallel

58
Q

Write the two equations for calculating p.d.

A
59
Q
A
60
Q

What is resistance?

A

The opposition of a conductor to the flow of electric current.

61
Q

How is electrical resistance measured?

A

In ohms

62
Q

Tell me the equation of resistance.

A
63
Q
A
64
Q

How do you measure the magnitude of resistance?

A
  1. Measure the voltage drop across a resistance in a circuit with a voltmeter and the current through the resistance with an ammeter. Use ohm’s law eqn to find resistance.
65
Q

Draw the graph of an ohmic conductor.

A
66
Q

What is an ohmic conductor?

A

A conductor that obeys ohms law.
Current is directly proportional to the voltage in ohmic conductors

67
Q

Draw the graph of a non-ohmic conductor

A
68
Q

Draw the graph of a diode.

A
69
Q

What type of conductor is a diode?

A

A non-ohmic conductor. It conducts in one direction only

70
Q

List the factors that affect the resistance of a wire.

A

The longer a wire, the greater its resistance
The greater the diameter, the less resistance
The material the wire is made from

71
Q

Write the equation for the resistance of a wire.

A
72
Q
A
73
Q

How do you calculate power through a circuit?

A

P = VI

74
Q

What is electric power?

A

The energy per unit time converted by an electric circuit into another form of energy

75
Q
A
76
Q

How do you calculate electrical energy?

A

E = Pt
E = IVt

77
Q
A
78
Q

How do you calculate the cost of electricity?

A
79
Q
A
80
Q

Draw the symbols for:
Single cell
Multiple Cells (battery)
DC Voltage source
AC Voltage source

A
81
Q

Draw the symbol for:
Open switch
Closed switch

A
82
Q

Draw the symbol for a fixed resistor

A
83
Q

Draw the symbol for a variable resistor

A
84
Q

Draw a Heater

A
85
Q

Draw a thermistor

A
86
Q

Draw a light dependent resistor.

A
87
Q

Draw a lamp.

A
88
Q

Draw an ammeter

A
89
Q

Draw a voltmeter

A
90
Q

Draw a galvanotmeter

A
91
Q

Draw a magnetising coil (inductor)

A
92
Q

Draw a transformer

A
93
Q

Draw a bell

A
94
Q

Draw a fuse

A
95
Q

Draw a relay

A
96
Q

Draw a generator

A
97
Q

Draw a motor

A
98
Q

Draw a diode and a light emitting diode

A
99
Q

What is a diode?

A

An electrical device allowing current to move only in one direction

100
Q

How much resistance does an ideal diode have?

A

Zero resistance in the direction which allows current to flow.
Infinite resistance in the reverse direction

101
Q

What is forward bias?

A

If a potential difference is applied across a diode in the direction with low resistance, it is said to be forward bias.

102
Q

What is reverse bias?

A

If a potential difference is applied in the direction with very high resistance, it is said to be reverse bias

103
Q

What happens if the reverse bias potential difference is too high?

A

A diode may break down and the current becomes infinites, resulting in a short circuit

104
Q

What is PIV rating?

A

The maximum reverse-bias voltage that a diode can withstand without ‘breaking down’

105
Q

Draw a series circuit.

A
106
Q

List the features of a series circuit.

A
  1. The current through each of the components is the same.
  2. The voltage across the circuit is the sum of the voltages across each component
  3. If you put more lamps into a series circuit, the lamps will be dimmer than before
  4. If one component is fused, then the other components of the circuit will not be functional
  5. They are useful if you want a warning that one of the components in the circuit has failed.
107
Q

Write the eqn for the total current in a series circuit.

A

Total current = I1 = I2 = I3

108
Q
A
109
Q

Write the eqn for the p.d in a series circuit.

A

This relationship expresses the law of conservation of energy

110
Q
A
111
Q
A
112
Q

How do you calculate total resistance in a series circuit?

A
113
Q
A
114
Q

Draw a parallel circuit.

A
115
Q

List the features of a parallel circuit.

A
  1. The voltage across each of the components is the same.
  2. The total current is the sum of the currents through each component
  3. If a lamp breaks or a component is disconnected the other components keep working
  4. The lamps remain bright is you add more lamps
  5. Useful if you want components to continue to work even if one component has failed.
116
Q

Write the eqn for the current in a parallel circuit.

A
117
Q
A
118
Q

Write the eqn for the p.d in a parallel circuit.

A
119
Q
A
120
Q

Write the eqn for the total resistance.

A
121
Q
A
122
Q
A

IGCSE Physics (21 decks)

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