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BMAT > Physics > Flashcards

Physics Flashcards

1
Q

How does an insulator become charged?

A

Electrons are transferred from one material to another by friction

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2
Q

What is charging caused by?

A

A loss or gain of electrons

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3
Q

What is important to remember about like charges?

A

They will repel

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4
Q

What is important to remember about unlike charges?

A

They attract

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5
Q

What happens when an appliance short circuits?

A

The live wire of an appliance touches the neutral wire

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6
Q

What is an earth wire used for?

A

If there is a fault in the circuit, the earth wire carries the charge into the ground

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7
Q

Circuit symbol for a cell

A

A longer vertical line parallel to a shorter parallel line on the right

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8
Q

Circuit symbol for a battery

A

Multiple cells joined together

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9
Q

Circuit symbol for lamp

A

Circle with a cross inside

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10
Q

Circuit symbol for a resistor

A

A clear rectangle

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11
Q

Circuit symbol for variable resistor

A

A rectangle with a diagonal arrow pointing from bottom left to top right

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12
Q

Circuit symbol for ammeter

A

Circle with an A inside

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13
Q

Circuit symbol for voltmeter

A

Circle with a V inside

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14
Q

Circuit symbol for switch

A

Two circles connected by a straight line

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15
Q

Circuit symbol for diode

A

A circle with a triangle and straight line inside

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16
Q

What is the difference between direct and alternating current?

A

An alternating current repeatedly reverses direction

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17
Q

What is the difference between conductors and insulators?

A

A conductor allows energy to pass through it whereas an insulator doesn’t

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18
Q

Examples of conductors

A

Copper and aluminium

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19
Q

Examples of insulators

A

Plastics and rubber

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20
Q

Equation for current

A

Charge flow / time

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21
Q

What are voltmeters used for?

A

Measures the potential difference across a component

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22
Q

Equation for resistance

A

Potential difference / current

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23
Q

What does the V-I graph for a fixed resistor look like?

A

A diagonal line from bottom left to top right directly through the origin

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24
Q

What does the V-I graph for a filament lamp look like?

A

A curve from bottom left to top right passing directly through the origin

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25
Q

Properties of LDRs

A

Resistance decreases with light intensity

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26
Q

Properties of ideal diodes

A

Allows the current to flow in one direction only

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27
Q

What are the rules for current in a series circuit?

A

The same current passes through each component

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28
Q

What are the rules for voltage in a series circuit?

A

The total potential difference is shared between the components

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29
Q

How to calculate the total resistance in a series circuit?

A

Add the resistances of each component

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30
Q

What are the rules for current in a parallel circuit?

A

The total current is the sum of the currents passing through the branches

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31
Q

What are the rule for potential difference in a parallel circuit?

A

The potential difference across each component is equal

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32
Q

Why is the total resistance in a parallel circuit less than that of any individual resistor?

A

The potential difference remains the same. Adding a resistor increases the current entering the system
Resistance = p.d./i so resistance decreases

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33
Q

Equation for voltage

A

Energy transferred / charge flow

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34
Q

What are the two equations for power?

A

Current x voltage

Current^2 x resistance

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35
Q

What does energy transferred equal?

A

Power x time

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36
Q

What is the north pole of a magnet?

A

The end of the magnet that will always point north

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37
Q

What is the south pole of the magnet?

A

The end of the magnet that will always point south

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38
Q

What is attraction?

A

The force between two unlike poles

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39
Q

What is repulsion?

A

The force between two like poles

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40
Q

Describe the magnetic field around a magnet

A

Lines point in a direction away from the north pole towards the south, the magnetic field is more concentrated at the poles

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41
Q

What is the difference between soft and hard magnets?

A

Hard magnetic retain their magnetism and are difficult to demagnetize, soft magnetic materials are easy to demagnetize

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42
Q

Describe induced magnetism

A

An unmagnetized material can be magnetized by placing it inside a magnetic field

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43
Q

What is the difference between permanent and electromagnetism?

A

A permanent magnet retains its magnetism over a long period of time, whereas electromagnets can be magnetised and demagnetised

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44
Q

How to increase the magnetic field of a solenoid

A

Increase the strength of the current

Can reverse its direction by reversing the direction of the current

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45
Q

Characteristics of solids

A

Particles are tightly packed

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46
Q

Characteristics of liquids

A

Particles are packed together but less tightly than solids. Liquids take on the shape of their container

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47
Q

Characteristics of gases

A

Particles are held together loosely

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48
Q

What is the effect of temperature on particles?

A

The particles move faster with more kinetic energy and collide more frequently

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49
Q

What is the effect of pressure on particles?

A

The particles are held closer together so collide more often

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50
Q

At constant temperature, what will both pressure and volume be?

A

Constant

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51
Q

What is melting point?

A

The temperature at which a solid melts

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52
Q

What is boiling point?

A

The temperature at which a liquid turns into a gas

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53
Q

What is the latent heat of fusion?

A

The amount of heat energy required to change 1g of a substance from the solid to liquid state without changing its temperature

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54
Q

What is latent heat of vaporisation?

A

The amount of energy required to change 1g of a substance from the liquid to gaseous state without changing its temperature

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55
Q

Equation for density

A

Mass / volume

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56
Q

What happens to density as you move from solid to gas?

A

It decreases

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57
Q

How do you determine density experimentally?

A

The amount of water displaced when an object is placed in a body of water is its volume. Use this and its mass to calculate density

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58
Q

Equation for pressure

A

Force / area

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59
Q

Equation for hydrostatic pressure

A

h x p x g
h = Height of column
p = density of liquid
g = acceleration of gravity

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60
Q

Equation for hydrostatic pressure

A

h x p x g
h = Height of column
p = density of liquid
g = acceleration of gravity

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61
Q

What are thermal conductors?

A

Materials that allow heat to travel through them

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62
Q

What are thermal insulators?

A

Materials that don’t allow heat to travel through them

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63
Q

Examples of thermal conductors

A

Steel, copper, aluminium

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64
Q

Examples of thermal insulators

A

Plastic, wool, foam

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65
Q

What factors affect the rate of conduction?

A

Temperature difference across the material
Thickness of material
Thermal conductivity of material

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66
Q

What impact does temperature have on the density of fluid?

A

Increasing temperature = increased volume = decreased density

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67
Q

What will happen to a wire carrying a current in a magnetic field?

A

It will experience a force

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68
Q

How to remember the factors affecting the direction of a force on a wire?

A

The left hand rule - first finger = field

  • thumb = movement
  • second finger = current
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69
Q

What are the factors affecting the direction of a force on a wire in a magnetic field?

A

Magnetic field and current

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70
Q

What are the factors affecting the magnitude of a force on a wire in a magnetic field?

A

Size of current, strength of magnet

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71
Q

How do you calculate the force on a wire?

A

Force = magnetic flux density x current x length

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72
Q

How is a dc motor constructed?

A

A coil rotates inside a magnetic field
An electric current is induced
The output comes via split ring output
As the coil turns, the split-ring commutator reconnects The coil the opposite way around each the circuit each half turn
This means that the wire will only be connected to one half of the output
Therefore, the current flows in one direction only

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73
Q

What are electromagnets used in

A

Cranes, motors, doorbells

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74
Q

When will a voltage be induced in a wire?

A

When a wire cuts a magnetic field

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75
Q

How does an ac generator work?

A

The movement of the bar magnet induces a p.d. in the coil

This p.d. creates a current because the coil is part of a complete circuit

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76
Q

When will the outcome of the generator be highest?

A

When the plane of the coil is parallel to the magnetic field
Use a magnet with a strong magnetic field
More turns on the coil of wire

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77
Q

What will the graph of an ac generator look like?

A

A sin graph

78
Q

What is a step up transformer?

A

Increase the size of an alternating potential difference

79
Q

What is a step down transformer?

A

Decreases the size of an alternating potential difference

80
Q

What is the voltage ratio for transformers?

A

Coils on 1 / coils on 2 = voltage on 1 / voltage of 2

81
Q

What is important about a transformer that is 100% efficient?

A

It is the total transfer of electrical power - VpIp = VsIs

82
Q

Why is it important that a transformer has a high voltage?

A

Reduces energy lost in resistance

83
Q

What is a scalar quantity?

A

Has only magnitude

84
Q

What is a vector quantity?

A

Has both magnitude and direction

85
Q

What is the difference between speed and velocity?

A

Speed is a scalar quantity, velocity is a vector

86
Q

What is the difference between distance and displacement?

A

Distance is a scalar quantity, displacement is a vector

87
Q

Equation for speed

A

Distance / time

88
Q

Equation for velocity

A

Change in displacement / time

89
Q

Equation for acceleration

A

Change in velocity / time

90
Q

What is the gradient of a distance-time graph?

A

Speed

91
Q

What is the gradient of a displacement-time graph?

A

Velocity

92
Q

What is the gradient of a speed-time graph?

A

Acceleration

93
Q

What is the area under a speed-time graph?

A

Distance travelled

94
Q

What is the gradient of a velocity-time graph?

A

Acceleration

95
Q

What is the area under a velocity-time graph?

A

Displacement

96
Q

What does average speed equal?

A

Total displacement / total time

97
Q

What is the equation of motion?

A

v^2 - u^2 = 2as

98
Q

What are the different forces?

A

Weight, normal contact, drag, friction, magnetic, electrostatic, thrust, upthrust, tension and lift

99
Q

What does work equal?

A

Force x distance

100
Q

What is work done?

A

Transfer of energy

101
Q

What does gravitational potential energy equal?

A

Mass x gravitational field strength x height

102
Q

What does kinetic energy equal?

A

.5 x mass x velocity^2

103
Q

What is the law of the conservation of energy?

A

Energy can’t be created or destroyed, only transformed from one form to another

104
Q

What is wasted energy?

A

Energy that isn’t used in the way that it was intended to

105
Q

Equation for percentage efficiency

A

(useful output/total output) x 100

106
Q

What does frequency equal?

A

1 / period

107
Q

What does wave speed equal?

A

Distance / time or frequency x wavelength

108
Q

Where are neutrons and protons found?

A

The nucleus

109
Q

Where are electrons found?

A

Orbitals

110
Q

Charge and mass of neutron

A

0, 1

111
Q

Charge and mass of proton

A

1, 1

112
Q

Charge and mass of electron

A

Very small, 1/2000

113
Q

What is ionisation caused by?

A

Gain/loss of electrons

114
Q

Where do emissions arise from?

A

An unstable nucleus

115
Q

What is an atom’s half life?

A

The time taken for half of the unstable nuclei to decay

116
Q

Properties of diodes

A

No resistance, only allows the current to flow in one direction

117
Q

Properties of thermistors

A

Resistance decreases with increasing temperature

118
Q

Properties of LDRs

A

Resistance decreases with increasing light intensity

119
Q

What does the magnetic field pattern around a solenoid look like?

A

Each field line is a complete loop which bends from one side of the solenoid to the other

120
Q

What is the resultant force?

A

The effect of multiple forces on an object written as a single force

121
Q

What does the gradient of a force-extension graph equal before the limit of proportionality is reached?

A

The spring constant

122
Q

What is the elastic limit?

A

The point at which a spring has been so stretched so much it won’t return to its original shape

123
Q

What is Hooke’s law?

A

The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length

124
Q

Equation for Hooke’s law

A

Force = k x Δl

125
Q

Equation for elastic energy

A

.5 x k x x^2

126
Q

What is Newton’s first law?

A

A body will remain at rest or travel uniformly unless acted on by a resultant external forc

127
Q

What property can change an object’s inertia?

A

Mass

128
Q

What is Newton’s second law?

A

Force = mass x acceleration

129
Q

What is Newton’s third law?

A

Two objects exert equal and opposite forces on eachother

130
Q

Equation for momentum

A

Mass x velocity

131
Q

Equation for force when using momentum

A

Force = change in momentum

132
Q

What is the law of the conservation of momentum?

A

The momentum before a collision = the momentum after

133
Q

What is the value of gravitational field strength?

A

10 N/kg

134
Q

Equation for weight

A

Weight = mass x gravitational field strength

135
Q

What is the difference between mass and weight?

A

Weight is the force exerted by gravity on an object

136
Q

What is terminal velocity?

A

The velocity reached on an object when the drag force is equal and opposite to the force making it move

137
Q

What factors affect terminal velocity?

A

The object’s mass and surface area

Gravitational field strength

138
Q

What is free-falling acceleration

A

An object falling purely under the force of gravity

139
Q

What will happen to an object’s temperature when energy is transferred to/from it?

A

It will increaese/decrease

140
Q

Equation for specific heat capacity

A

Thermal energy / (mass x Δtemperature)

141
Q

What electromagnetic waves are involved in thermal radiation?

A

Infrared

142
Q

What material is good at absorbing radiation?

A

A light coloured/shiny one

143
Q

What factors affect the rate of emission/absorption?

A

The surface area, volume and material of an object

144
Q

What is the equation for specific latent heat?

A

Energy / mass

145
Q

Equation for specific heat capacity

A

m x c x Δt

146
Q

What happens when waves are reflected at a surface?

A

The reflected ray is at the same angle as the incident ray

147
Q

What happens when waves refract at a boundary?

A

The waves change both speed and direction

148
Q

What effect does reflection have on frequency, wavelength and direction?

A

Frequency: same
Wavelength: same
Direction: same

149
Q

What effect does refraction have on frequency, wavelength and direction?

A

Frequency: same
Wavelength: decreases
Direction: bends towards normal

150
Q

What is the doppler effect?

A

The change in distance between causer and observer causes a change in frequency and wavelength

151
Q

What does the angle of incidence equal?

A

The angle of reflection

152
Q

What is nuclide notation?

A 
A(X)
Z
Contains Z protons and A-Z neutrons
Atomic mass = A
Charge = +Ze
153
Q

How far can alpha radiation penetrate?

A

It is blocked by paper

154
Q

How far can beta radiation penetrate?

A

Blocked by aluminium foil

155
Q

How far can gamma radiation penetrate?

A

Blocked by thick lead sheet

156
Q

Rank the three types of radiation from highest ionising power to weakest

A

Alpha, beta, gamma

157
Q

Where does background radiation come from?

A

Radon gas

158
Q

What is an alpha particle made from?

A

2 protons and 2 neutrons

159
Q

What is a beta particle made from?

A

An electron

160
Q

What is gamma radiation made from?

A

Waves

161
Q

What effect does alpha radiation have on atomic number?

A

Its atomic number decreases by 2

Its mass number decreases by 4

162
Q

What effect does beta radiation have on atomic number?

A

The atomic number increases by 1

163
Q

What effect does gamma radiation have on atomic number?

A

None

164
Q

Which types of radiation can be deflected by electric fields?

A

Alpha and beta radiation

165
Q

Give two properties of electromagnetic waves

A

They are transverse waves and travel at the speed of light in a vacuum

166
Q

What are the seven components of the spectrum?

A

Radio waves, microwaves, IR, visible light, ultraviolet, x-rays, gamma rays

167
Q

Give the wavelengths and frequencies of the component parts of the electromagnetic spectrum

A 
Radio waves: 10^3 and 10^4
Microwaves: 10^-2 and 10^8
IR: 10^-5 and 10^12
Visible light: 10^-6
Ultraviolet: 10^-8, 10^15
X-rays: 10^-10 and 10^18
Gamma rays: 10^-12 and 10^20
168
Q

What are produced by reflections?

A

Echoes

169
Q

What is the range of human hearing?

A

20Hz to 20kHz

170
Q

How is volume related to amplitude?

A

Volume is proportional to amplitude

171
Q

How is pitch related to frequency?

A

They are directly proportional

172
Q

How do ultrasounds measure internal boundaries?

A

When there is a boundary, some ultrasound is reflected back. The time taken is recorded and this is used to work out how far the boundary is

173
Q

How are ultrasounds used for medical imaging?

A

Wherever there is a boundary, some of the wave is reflected back and detected
The timing and distribution of these echoes are recorded and turned into an image

174
Q

Why is a medium needed for sound?

A

Sound molecules vibrate and pass the impulse between one another; this can’t happen in a vacuum

175
Q

How are sound waves produced?

A

An object vibrates and transfers this energy to another medium

176
Q

What is the amplitude?

A

The height of a wave

177
Q

What is the frequency?

A

The number of oscillations in a given time

178
Q

What is the wavelength?

A

The difference between crests in successive waves

179
Q

What is the period?

A

The time taken for one complete wave

180
Q

What is the peak?

A

The highest point on a wave

181
Q

What is the trough?

A

The lowest point on a wave

182
Q

What is a compression?

A

The wave is compressed

183
Q

What is a rarefaction?

A

The wave is stretched

184
Q

What is important to remember about waves?

A

They transfer energy without the movement of matter

185
Q

What are transverse waves?

A

The oscillations are perpendicular to the direction of energy transfer

186
Q

What are longitudinal waves?

A

The oscillations are parallel to the direction of energy transfer

187
Q

Examples of transverse waves

A

Electromagnetic waves

188
Q

Examples of longitudinal waves

A

Sound waves

189
Q

What properties make a good electrical conductor?

A

Low first ionisation energy, simple material structure

190
Q

How to calculate total resistance in parallel?

A

1/R1 + 1/R2 + 1/R3 etc

191
Q

What is important to remember about the pressure in a hydraulic system?

A

It is always constant

192
Q

Volume of a sphere

A

4/3 x pi x r^3

BMAT (3 decks)

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