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physics definitions Flashcards

1
Q

A physical quantity

A

A quantity that can be measured. Consists of a magnitude and a unit

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2
Q

Oscillation

A

A complete to-and-fro motion of an object

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3
Q

Period of a simple pendulum

A

Period of a simple pendulum is the time taken for one complete oscillation

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4
Q

Scalar quantities

A

They are physical quantities that only have magnitude

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5
Q

Vector quantities

A

Are physical quantities that have both magnitude and direction

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6
Q

Speed

A

Distance moved per unit time

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7
Q

Velocity

A

Rate of change of displacement

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8
Q

Acceleration

A

Rate of change of velocity

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9
Q

What does the gradient of a displacement-time graph give you?

A

Velocity of the object

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10
Q

What does the gradient of a velocity-time graph give you?

A

Acceleration of the object

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11
Q

How to find displacement?

A

Area under a velocity time graph

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12
Q

When does an object achieve terminal velocity?

A

When weight = air resistance

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13
Q

Newton’s first law of motion

A

States that every object will continue in its state of rest or uniform motion in a straight line, unless a resultant force acts on it.

This law is known as “inertia” - dependent on mass

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14
Q

Newton’s second law of motion

A

States that when a resultant force acts on an object of a CONSTANT MASS, the object will continue to accelerate in the direction of the resultant force. Product of mass and acceleration gives the resultant force

F=ma

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15
Q

Newton’s third law of motion

A

States that if body A exerts a force Fab on body B, body B will exert an equal and opposite force Fba on body A.

For every action, there’s an equal and opposite reaction

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16
Q

Friction

A

Is the contact force that opposes or tends to oppose motion between surfaces in contact

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17
Q

Mass

A

It’s the amount of matter in a body

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18
Q

Weight

A

Weight of an object is the gravitational force or gravity acting on it

W=mg

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19
Q

Gravitational field

A

Is a region in which a mass experiences a force due to gravitational attraction

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20
Q

Gravitational field strength, g

A

Defined as the gravitational force acting per unit mass

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21
Q

Inertia of an object

A

The reluctance of an object to change its state of rest or motion, due to its mass

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22
Q

Density

A

Mass per unit volume

p=m/v

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23
Q

Moment of a force

A

Is the product of the force and perpendicular distance from the pivot to the line of action of the force

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24
Q

Principle of moments

A

When a body is in equilibrium, the sum of anti-clockwise moments about a pivot is equal to the sum of clockwise moments about the same pivot.

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25
Q

Centre of gravity

A

Is a point in which the weight of an object appears to act on

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26
Q

Stability

A

Is a measure of its ability to return to its original position even after being slightly displaced

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27
Q

The three types of equilibrium?

A
  1. Stable equilibrium
  2. Unstable equilibrium
  3. Neutral equilibrium
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28
Q

What is stability affected by?

A
  1. Base area
  2. Center of gravity
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29
Q

Energy

A

It’s the capacity to do work

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30
Q

Principle of conservation of energy

A

States that energy cannot be created not destroyed, it can only be converted from one form to another. Total energy in an isolated system remains constant

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31
Q

Work done

A

Work done by a Constant force of an object is the product of the force and the distance moved by the object in the direction of the force

Work done = force x distance moved in the direction of force

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32
Q

Power

A

Rate of work done or rate of energy conversion

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33
Q

Pressure

A

Force acting per unit area

P= F/A

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34
Q

Temperature

A

Refers to how hot or cold an object is

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35
Q

Heat

A

Amount of thermal energy that is being transferred from a hotter to a colder region

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36
Q

Kinetic model of matter

A

States that tiny particles that make up matter are always in continuous random motion

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37
Q

Relationship between pressure and temperature?

A

Directly proportional

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38
Q

Relationship between pressure and volume

A

Inversely proportional

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39
Q

Relationship between temperature and volume

A

Directly proportional

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40
Q

Thermal energy

A

Always flows from a region of higher temperature to a region of lower temperature. Net flow of thermal energy only occurs when there is a difference in temperature

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41
Q

Conduction

A

Is the transfer of thermal energy through a medium without any flow of the medium itself

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42
Q

Convection

A

Is the transfer of thermal energy by means of convection currents in a fluid (liquid or gas), due to the difference in densities

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43
Q

Radiation

A

It’s the transfer of thermal energy in the force of electromagnetic waves such as infrared radiation without the aid of a medium

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44
Q

Heat capacity C

A

It’s the amount of thermal energy required to raise the temperature of a substance by 1K or 1 degree celcius

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45
Q

SI Unit for Heat Capacity C?

A

JK-1 or JC-1

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46
Q

Specific heat capacity c

A

It’s the amount of thermal energy required to raise the temperature of a unit mass (1kg) of a substance by 1K or 1 degree celcius

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47
Q

Unit for specific heat capacity?

A

Jkg-1K-1 or Jkg-1C-1

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48
Q

Latent heat

A

It’s the energy released or absorbed by a substance during a change of state, without a change in its temperature

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49
Q

Latent heat of fusion

A

The amount of thermal energy required to change a substance from solid to liquid state, without a change in temperature

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50
Q

SI Unit for latent heat of fusion

A

J (Joules)

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51
Q

SI Unit for latent heat of fusion

A

J (Joules)

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52
Q

Specific latent heat of fusion

A

The amount of thermal energy required to change a unit mass (1kg) of a substance from a solid to liquid state, without a change in temperature

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53
Q

SI Unit for specific latent heat of fusion?

A

Jkg-1

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54
Q

Latent heat of vaporisation

A

is the amount of thermal energy requires to change a substance from liquid state to gaseous state, without a change in temperature.

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55
Q

SI Unit for latent heat of vaporisation

A

J (Joules)

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56
Q

Specific latent heat of vaporisation

A

is the amount of thermal energy required to change a unit mass (1kg) of a substance from liquid state to gaseous state, without a change in temperature.

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57
Q

SI Unit for specific latent heat of vaporisation?

A

Jkg-1

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58
Q

First law of reflection

A

States that the incident ray, reflected ray, and the normal at the point of incidence all lie in the same plane

59
Q

Second law of reflection

A

States that angle of incidence i is equal to the angle of reflection r (i=r)

60
Q

Refraction

A

It’s the bending of light as light passes from one optical medium to another

61
Q

First law of refraction

A

Incident ray, refracted ray, and the normal, all lie in the same plane

62
Q

Second law of refraction

A

States that for two given media, the ratio of the sine of angle of incidence i to the sine of the angle of refraction r is a constant

sini/sinr = n

63
Q

Critical angle c

A

Defined as the angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is 90 degrees

64
Q

Total internal reflection

A

Is the complete reflection of a light ray inside an optically denser medium at its boundary with an optically less dense medium

65
Q

Focal length

A

is the distance between the optical centre and the focal point

66
Q

Source of a wave

A

Is a vibration or oscillation

67
Q

What do waves do?

A

They transfer energy from one point to another without transferring the medium

68
Q

Transverse waves

A

Are waves that travel perpendicular to the direction of the vibration

69
Q

Longitudinal waves

A

Waves that travel parallel to the direction of the vibration

70
Q

Amplitude A

A

of a wave is the maximum displacement of a point from its rest position

71
Q

Wavelength

A

It’s the shortest distance between two points in a phase

72
Q

Period T of a wave

A

It’s the time taken to produce one complete wave

73
Q

Frequency f of a wave

A

Is the number of complete waves produced per second

Units: Hz

74
Q

Wave speed

A

Is the distance travelled by a wave per second

75
Q

Wavefront

A

It’s an imaginary line on a wave that joins all adjacent points that are in a phase

76
Q

Sound

A

It’s a form of energy that is transferred from one form to another as a longitudinal wave

77
Q

Echo

A

It’s the repetition of a sound due to the reflection of sound

78
Q

Ultrasound

A

Is sound with frequencies above the upper limit of human range of audibility

79
Q

Pitch is related by the?

A

Frequency of a sound wave. Higher the frequency, higher the pitch

80
Q

Loudness is related to the?

A

Amplitude of a sound wave, the larger the amplitude, the louder the sound

81
Q

Electric force

A

Is the attractive or repulsive force that electric charges exert on one another

82
Q

Electric field

A

Is a region in which an electric charge experiences an electric force

83
Q

Direction of an electric field

A

Is the direction of the force that would act on a small positive charge

84
Q

The strength of an electric field

A

Is indicated by how close the field lines are to one another

85
Q

Conventional current

A

Is in the opposite direction to electron flow

86
Q

Electric current

A

Is the rate of flow of electric charge Q

I = Q/t

87
Q

Electromotive force (emf) of an electrical energy source

A

Is the work done by the source in driving a unit charge around a complete circuit

88
Q

Potential difference (p.d) across a component in an electric circuit

A

Is the work done to drive a unit charge through the component

89
Q

Resistance R of a component

A

Is the ratio of the potential difference V across it to the current I flowing through it

V=IR

90
Q

Ohms law

A

States that the current passing through a metallic conductor is DIRECTLY proportional to the potential difference across the component, provided that physical conditions such as temperature remains constant

91
Q

Potential divider

A

Is a line of resistors connected in series but is used to provide a fraction of the voltage of a source to another part of the circuit

92
Q

Input transducers

A

Are electronic devices that convert non-electrical energy to electrical energy

93
Q

Magnetic materials

A

Are materials that can be attracted to a magnet

(COINS)
Cobalt
Iron
Nickel
Steel

94
Q

Non-magnetic materials

A

are materials that cannot be attracted to a magnet

95
Q

Magnetic induction

A

Is the process whereby an object made of a magnetic material becomes a magnet when it is near or in contact with a magnet

96
Q

A magnetic field

A

Is the region surrounding a magnet, in which a body of magnetic material experiences a magnetic force

97
Q

What is meant by an alternating current

A

An alternating current is an electric current that changes ita magnitude and direction of flow with time

98
Q

Efficiency

A

Ratio of the useful power/energy output to the total power/energy input X 100%

99
Q

Refractive index

A

It’s the ratio of the speed of light in vacuum to the speed of light in a medium

Or the ratio of the sine of angle of incidence in a vacuum to the sine of angle of refraction in a medium

100
Q

What can radio waves be used for

A

-Radio broadcasting
- television communications

101
Q

What can microwaves be used for

A

-microwaves, to heat food
-satellite television
- Global Positioning System GPS
- mobile phone networks

102
Q

What can infrared radiation be used for

A

-remote controllers
- ear thermometers
- intruder alarms
- infrared photographs

103
Q

What can visible light be used for

A

-optic fibres
- laser light

104
Q

what can Ultraviolet rays be used for

A
  • Sterilise surgical instruments
  • artificial suntanning
  • detection of forgery in bank notes
105
Q

what can X rays be used for

A
  • kill cancer cells (radiation therapy)
  • used in diagnostic tools in medicine and dentistry to observe for cracks and fractures
  • airport security, inspecting insides of luggages
106
Q

what can Gamma rays

A
  • sterilise medical equipment
  • kill cancer cells
107
Q

what happens From radio to gamma rays?
(R M I V U X G)

A

Wavelength decreases, frequency increases

108
Q

Kinetic energy is always related to?

A

Temperature

109
Q

Why should the fuse and switch be connected to the live wire? (USUALLY FUSE FIRST THEN SWITCH)

A

When the fuse is blown or switch is opened, the appliance will then be disconnected from the high potential of the live wire. This appliance will not be “live” as there is no current flowing through the appliance and it is safe to touch, prevents someone from getting an electric shock

110
Q

What is the purpose of a live wire

A

It’s connected to a high voltage and delivers current to the appliance. This is the wire to which circuit breakers, fuses, and switches are fitted

111
Q

What’s the purpose of the neutral wire

A

It completes the circuit by providing a return path to the supply for the current, it’s usually at 0 volts

112
Q

What’s the purpose of an earth wire

A

It is a low resistance wire and it is usually connected to the metal casing of appliances

If an electrical fault results in the live wire touching the metal casing, the earth wire is able to allow large currents to flow to the ground, which has a much lower resistance than the person. Hence preventing an electrical shock.

113
Q

Why is the earth wire usually thick?

A

Bigger cross sectional area = lower resistance

114
Q

why is there an output voltage produced in the secondary coil?

A

because of the alternating current, it produces a changing magnetic field around it. this means that there is a change in magnetic flux linkage the secondary coil and hence by faradays law, an emf is produced

115
Q

what’s the split ring commutator for?

A

it reverses the current direction in the coil every half a turn and allows the coil to constantly turn in ____(upward/downward) direction. third it rotates in an (anti clockwise / clockwise) direction continuously

116
Q

what are slip rings for?

A

to allow firm contact between coil and the 2 carbon brushes such that there is constant contact to allow the current to flow to the external circuit. the direction of the induced current produced will be alternating

117
Q

order of resistivity from lowest to highest

A

-silver
-copper
- aluminium
- tungsten
- nichrome

SCATN
strong clever awesome talented nice

118
Q

what happens to the speed of light from a less dense to denser medium? how does it bend?

A

bends towards normal, speed of light decreases

119
Q

what happens to the speed of light from a denser to a less dense medium? how does it bend?

A

bends away from normal, speed of light increases

120
Q

explain conduction

A

conduction is the process by which thermal energy is transmitted through a medium caused by molecular vibrations.

when ___ it is heated, the atoms gain kinetic energy and vibrate faster about in their fixed positions. the atoms collide with the less energetic neighbouring atoms resulting in the transfer of kinetic energy from a region of higher temperature to a region of lower temperature. this process continues until they all possess the same amount of thermal energy

** thermal energy is transferred through the increase in vibration and hence the kinetic energies of the atoms**

*talk about how they’re closely packed and vibrate about their fixed positions**

121
Q

why does conduction occur better in metals?

A

conduction is far better in metals because they contain many free electrons that are able to move freely among the atoms of the metal

(there is collision of the vibration of atoms and free moving electrons)

when heated, free mobile electrons gain energy and move vibrate and move more vigourously. since these mobile electrons are free to travel in spaces between the atoms to transfer energy

122
Q

explain convection currents in liquids

A

if the air gains heat, it will expand and become less dense

if air does not gain heat, it’s considered as “colder air” which is denser than hot air

hot air rises and cold air sinks to replace the hot air, this sets up a convection current due to the difference in densities

this process repeats ( cold air gains heat bla bla bla)

thus there is a transfer of thermal energy from convection

123
Q

factors affecting radiation?

A

surface temperature
- hotter an object, higher the energy emission

surface area
- larger s.a, higher rate of energy transfer

surface colour and texture
- rough, dull, black is a better emitter and absorber of infrared radiation

124
Q

What does a current carrying conductor do

A

It produces a magnetic field around it

125
Q

What happens when the current is reversed in a current carrying wire?

A

The direction of the magnetic field is reversed

126
Q

What happens when current increases in a current carrying wire?

A

Strength of magnetic field increases

127
Q

How the the strength of the magnetic field of a flat coil be increased?

A

Increase the current flowing through the coil

128
Q

The magnetic field strength of a solenoid can be increased by

A

Increasing the current flowing through the solenoid

Increasing number of turns per unit length of the solenoid

Placing a soft iron core within the solenoid to concentrate the magnetic field lines

129
Q

What is the motor effect?

A

It is when a current carrying conductor is placed in a magnetic field, the conductor will experience a force

130
Q

What happens when we reverse the current or magnetic field in a current carrying conductor

A

The direction of the force on a current carrying conductor is reversed when we reverse the direction of current or magnetic field

131
Q

What is FLHR used for

A

To find The direction of the force on a current carrying conductor in a magnetic field

132
Q

Conductors carrying currents in the same direction

A

Attract

133
Q

Conductors carrying currents in opposite directions

A

Repel

134
Q

Electrons flow with current?

A

Opposite

135
Q

The turning effect on a current carrying conductor can be increased by:

A

Increasing the number of turns in the wired coil

Increasing the current in the wire coil

136
Q

The turning ever on a current carrying conductor in a DC motor can be increased by

A

Inserting a soft iron core into the coil

Increasing the number of turns in the coil

Increasing the current in the coil

137
Q

Definition of electromagnetic induction

A

It is the process through which an induced emf is produced in a conductor due to changing magnetic field

138
Q

Faradays law of electromagnetic induction

A

The magnitude of the induced emf in a circuit is directly proportional to the rate of change of magnetic flux in a circuit

139
Q

Lenz law

A

States that the direction of the induced emf, and hence the induced current in a closed circuit, is always such that it’s magnetic effect opposes the motion or change producing it

140
Q

An alternating current generator

A

Is a mechanical device that uses electromagnetic inducton to convert mechanical energy into electrical energy

141
Q

A transformer

A

a device that can change a high alternating voltage to a low alternating voltage

142
Q

What happens if we double the turns on the coil? (AC generator)

A

Doubling the number of turns would double the induced EMF ( max output voltage)

143
Q

What happens if a e double the frequency/the speed of the turns in an AC generator

A

It will double the induced emf and also increase the frequency (period will be shorter)

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