100 or so IGCSE Physics things to learn Flashcards
1
Q
Why do different planets have different values of g (gravitational field strength)
A
Planets with more mass (e.g. Jupiter) have a higher value of g
2
Q
What is felt when a current-carrying wire is in a magnetic field?
A
A force is felt when a wire carries a current in a magnetic field
3
Q
What happens to the resistance of a thermistor as it is heated
A
High temperatures reduces the resistance of a thermistor
4
Q
Give the unit and unit symbol for
Power, P
A
watt (W)
5
Q
Give the unit and unit symbol for
Density, ρ
A
kilogram per metre cubed (kg/m3)
6
Q
What component is this?
A
Bulb
7
Q
What does work done = energy transferred mean?
A
If you do 10J of work on a system you transfer 10J of energy to it.
8
Q
What materials does conduction happen best in and why?
A
Solids; particles are close together so can pass energy quickly. Works best of all in metals due to free electrons.
9
Q
What equation links;
weight, mass and gravitational field strength
A
weight = mass x gravitational field strength
10
Q
How would you find the volume of a small irregular object (e.g. a pebble)
A
submerge in water. The volume of water displaced = volume of pebble
11
Q
How does a fuse work
A
When the current goes higher than the value of the fuse it melts. This breaks the circuit and stops current flowing
12
Q
Give a use for x-rays
A
looking at the insides of things (medical imaging and other objects)
13
Q
Give the unit and unit symbol for
Acceleration, a
A
metre per second squared (m/s/s, m/s2)
14
Q
How would you find the volume of a regular object (e.g. a cube of metal)
A
measure each side (with ruler) and multiply together
15
Q
What equation links;
pressure, force and area
A
pressure = force ÷ area
16
Q
When a gas or liquid is at rest, what can you say about the pressure?
A
at a given depth, pressure in a fluid at rest acts equally in all directions
17
Q
Describe a longitudinal wave and give an example
A
Longitudinal waves travel parallel to the oscillation which caused them. E.g. sound
18
Q
Give a use for radio
A
Communictions and broadcast
19
Q
What are the energy transfers involved with nuclear power
A
nuclear ⇒ thermal ⇒ kinetic ⇒ electrical
20
Q
Give a danger and use for microwaves
A
Danger = internal heating of body tissue,
Use = cooking and satellite communications
21
Q
What equation links;
charge, current and time
A
charge = current x time
22
Q
Give a danger and use for ultra violet
A
Danger = blindness and damage to surface cells,
Use = flourescent lamps, security markings
23
Q
What is a magnetic field line?
A
A magnetic field line shows the direction of a magnetic field (N to S). Where lines are close together the field is strong.
24
Q
What happens to the current in a circuit when the resistance is decreased?
A
Current increases as resistance decreases
25
The gradient of a velocity-time graph gives
Acceleration
26
The gradient of a distance-time graph gives
Speed
27
Explain series circuits
Only one loop, simple, if one component fails no current flows
28
# What equation links;
refractive index, angle of incidence, angle or refraction
n = sin i ÷ sin r
refractive index = sin (angle of incidence) ÷ sin (angle of refraction)
29
The universe is made up of….
Billions of galaxies
30
# What equation links;
acceleration, change in velocity and time taken
acceleration = change in velocity ÷ time taken
31
Define the time period of a wave
Time period is how long it takes for a wave to pass a point
32
# What equation links;
work done, force and distance moved
work done = force x distance moved
33
What is the order of the EM spectrum
Radio, Microwave, Infra-red, Visible, Ultra-violet, X-ray & Gamma
34
When a wave is refracted what two things change
Speed and direction change during refraction
35
What is the difference between Alternating Current (AC) and Direct Current (DC)
DC (direct current) only flows in one direction. AC (alternating current) constantly changes direction.
36
# What equation links;
moment, force and perpendicular distance from pivot
moment = force x perpendicular distance from pivot
37
# Give the unit and unit symbol for
Charge, Q
coulomb (C)
38
What materials does convection happen best in and why
Fluids (gases and liquids); particles must be free to move so can't happen in a solid
39
# Give the unit and unit symbol for
Potential Difference, V
volt (V)
40
What component is this?
Thermistor
41
What is the force which opposes motion
Friction (e.g. against a road) or drag (e.g. moving through air)
42
# Give the unit and unit symbol for
Wavelength, λ
metre (m)
43
Factors which affect braking distance
Speed, weight of vehicle, quality of brakes and tryes, road surface
44
# Give the unit and unit symbol for
Pressure, p
pascal, newton per metre (Pa, N/m2)
45
# What equation links;
wave speed, frequency and wave length
wave speed = frequency x wave length
46
What are the energy transfers involved with water power
gravitational ⇒ kinetic ⇒ electric
47
Describe a transverse wave and give an example
Transverse waves travel at right angles to the oscillation which caused them. E.g. light, other EM waves, Mexican Waves
48
What are circuit breakers
Circuit breakers break the circuit when the current goes higher than a certain value. Unlike fuses, they can be reset once tripped.
49
How does convection produce wind?
Air is heated, expands, becomes less dense, rises, colder air rushes into the area of low pressure.
50
What is the relationship between force and extension for a spring
Force is directly proportional to extention (if force doubles extension doubles)
51
What do the thumb and fingers represent when using Flemming's Left Hand Rule?
thumb = force (direction of movement),
First Finger = Field,
seCond finger = Current
52
What makes something an elastic material
Material regains original shape once stretching force is removed
53
When the angle of incidence is less than the critical angle light is…
When the angle is less than the critical angle, light is refracted
54
Describe how thermal energy is transferred by radiation
Thermal radiation is an electromagnetic wave.
55
What is the frequency range for human hearing
20 Hz - 20 000 Hz
56
The initial linear part of a force-extension graph is linked to what law?
Hooke's Law (Force is directly proportional to extension)
57
Our local galaxy is called
The Milky Way
58
What component is this?
LDR (light dependent resistor)
59
When the angle of incidence is greater than the critical angle light is…
Totally internally reflected
60
What happens when current flows through a resistor
When current flows through a resistor it heats up (this effect is used in kettles and toasters etc.)
61
What materials does radiation happen best in and why?
Transparent (see through) materials; thermal radiation can be absorbed by some materials and pass through others.
62
Why does an object reach terminal velocity?
As the speed and drag increase, eventually weight = drag so no resultant force
63
Natural satellites (e.g. moons) and artificial satellites (e.g. Hubble) orbit what?
Planets
64
# What equation links;
energy transferred and work done
energy transferred = work done
65
Factors which affect thinking distance
Speed, awareness (tired, alcohol)
66
What are the energy transfers involved with fossil fuels
chemical ⇒ thermal ⇒ kinetic ⇒ electrical
67
# Give the unit and unit symbol for
Area, A
metre squared (m2)
68
Only appliances with what sort of case need an Earth wire?
Appliances with metal cases; if the live wire comes loose someone could get a shock without an Earth wire.
69
# What equation links;
gravitational potential energy, mass, g and height
gravitational potential energy = mass x g x height
70
What is the principle of conservation of energy
Energy cannot be created or destroyed; only changed from one form to another.
71
Where does the ray go next in each case?
72
# Give the unit and unit symbol for
Electric current, I
amp (A)
73
A galaxy is made up of…
Billions of stars
74
How would you describe a uniform field (3 marks)
Field lines are straight, parallel and equally spaced in a uniform field
75
Define frequency
Frequency is the number of waves going past a point per second
76
List the 5 types of non stored energies
Light, sound, thermal, kinetic, electrical
77
If a car has 20 000J of kinetic energy, how much work do the brakes have to do to stop the car?
20 000J
78
What is double insulation
Appliances with plastic cases are double insulated; even if live wire comes loose inside, a user can't be shocked
79
What component is this?
Diode
80
What happens to the current in series circuit as more bulbs are added?
More bulbs in series increases the resistance and decreases the current
81
What are the energy transfers involved with solar cells
light ⇒ electrical
82
The area under a velocity-time graph gives
Distance travelled
83
What part of the EM spectrum has the highest frequency (and energy)
Gamma has the highest frequency
84
What happens to the speed of an object as it falls?
What happens to its drag?
Speed increases (resultant force downwards)
drag increases
85
What are the energy transfers involved with solar heating systems
thermal ⇒ themal
86
Describe how thermal energy is transferred by conduction
Particles knock into each other and pass on the energy
87
If an object has 100J of gravitational potential energy when on a shelf and falls off, how much kinetic energy does it have just before hitting the floor? What have you assumed?
100J. But we assume there is no air resistance (100% efficient)
88
How can you see the shape **and** direction of a magnetic field
Use plotting compasses
89
# What equation links;
refractive index and critical angle
n = 1 ÷ sin c
refractive index = 1 ÷ sin (critical angle)
90
Refraction is when a wave………………………..
...bends
91
Name some electrical conductors (low resistance, allow current to easily flow)
Metal, graphite
92
Comets orbit what? What shapes are their orbits?
Comets orbit stars (e.g. the Sun) in elliptical orbits
93
What part of the EM spectrum has the longest wavelength
Radio has the longest wavelength
94
What is the law of reflection?
Angle of incidence = Angle of reflection
95
Define wavelength
Wavelength is the distance between two peaks or two troughs
96
# Give the unit and unit symbol for
Moment
newton metre (Nm)
97
How can you increase the speed of a motor (or volume of a speaker)?
Stronger magnet, more current
98
Give an example of an AC source and a DC source
Mains are an AC source. Batteries are DC sources
99
The rate of doing work is also known as?
Power
100
How do radiators in your house heat a room (hint, not by radiation)
Radiators heat air which rises and produces a convection current. Cold air is drawn into the bottom of the radiator too.
101
What is produced around a conductor when electrical current flows?
An electromagentic field is created when current flows
102
# What equation links;
efficiency, useful energy output and total energy input
efficiency = useful energy output ÷ total energy input
(also efficiency = useful energy output ÷ total energy output)
103
# Give the unit and unit symbol for
Frequency, f
hertz (Hz)
104
Describe how thermal energy is transferred by convection
Hotter regions of fluid expand, become less dense and float on colder regions
105
# Give the unit and unit symbol for
Length, l
metre (m)
106
Where does an objects weight always act
Through its centre of gravity
107
List the 4 types of stored (potential) energies
Gravitational, Elastic, Nuclear, Chemical
108
Why is the image in a mirror virtual?
The image in a mirror can't be projected onto a screen
109
What is the nature of an electric current in a metal conductor?
A flow of negatively charged electrons flowing from the negative side of a battery or power supply
110
What happens to the resistance of an LDR as more light is shone on it?
Bright light reduces the resistance of an LDR
111
Name some electrical insulators (high resistance, do not allow current to flow)
Plastic, wood, (pure) water
112
# What equation links;
force, mass and acceleration
force = mass x acceleration
113
Which way does light bend when it enters a material with a higher refractive index (e.g. air to glass)
Light bends towards the normal when it goes from air to glass
114
# What equation links;
density, mass and volume
density = mass ÷ volume
115
What is the critical angle
When ligh hits the boundary at the critical angle the angle of refraction is 90°
116
Forces can do what to an object?
Change speed, shape or direction
117
What is the efficiency of this machine
useful output energy = 10J
total input energy = 100J
efficiency = 10/100
= 0.1 or 10%
118
How can you prevent heat transfer by radiation?
Shiny surfaces are poor emitters. They also refelect the thermal radiation back.
119
Define amplitude
Amplitude is the maximum displacement above the equilibrium
120
# Give the unit and unit symbol for
Energy, E
joule (J)
121
# Give the unit and unit symbol for
Resistance, R
ohm (Ω)
122
What are the energy transfers involved with wind power
kinetic ⇒ electric
123
Planets orbit what? What shape are their orbits?
Planets orbit stars (e.g. the Sun) in circular orbits
124
One Watt is equal to what?
1 watt is 1 joule per second
125
What happens to the average speed of gas molecules as you heat a gas?
Average speed of gas molecules increases as you heat a gas
126
# What equation links;
pressure difference, height, density and g
pressure difference = height x density x g
127
Reflection is when a wave…………………………
...bounces off something
128
Electrical hazards include….
Frayed cables, damaged sockets, water near sockets and metal objects in sockets
129
Give a danger and use for infra red
Danger = skin burns,
Use = cooking and night vision equipment
130
# Give the unit and unit symbol for
Time, t
second (s)
131
# Give the unit and unit symbol for
Volume, V
metre cubed (m3)
132
What are meters X and Y?
X is a voltmeter (in parallel)
Y is an ammeter (in series)
133
# What equation links;
voltage, current and resistance
voltage = current x resistance
134
# What equation links;
kinetic energy, mass and speed
kinetic energy = 1/2 x mass x speed2
135
Give a danger and use for gamma
Danger = cancer, mutation,
Use = sterilising food and medical equipment
136
How can you show current is flowing in a circuit
A bulb or LED will light when a current flows. Or use an ammeter (in series)
137
How can you visualise the shape of a magnetic field (3 marks)
Place magnet under paper, sprinkle iron filings on top of paper, gently tap paper so filings line up with field lines.
138
What are the energy transfers involved with geothermal power
(nuclear) ⇒ thermal ⇒ kinetic ⇒ electric
139
How can you prevent heat transfer by convection?
Trap the fluids (e.g. trapping air in wool). This prevents both conduction and convection.
140
What component is this?
Wire
141
How can you produce a uniform magnetic field (3 marks)
Place two attracting bar magnet poles (N&S) close together, hold them in place to avoid them touching
142
# Give the unit and unit symbol for
Force, F
newton (N)
143
What component is this?
Diode
144
Explain parallel circuits
Several routes for current to take, allows components to be switched on individually (e.g. lights at home), components get full supply voltage
145
What is another name for the rate of flow of charge?
Current
146
Why aren't machines 100% efficient?
Typically some energy is lost to the surroundings as heat.
147
# Give the unit and unit symbol for
Velocity (initial, final), (u,v)
metre per second (m/s)
148
# Give the unit and unit symbol for
Temperature, T
kelvin (K)
149
What is the easiest way to reduce risk of injury from microwaves, infra red, ultra violet or gamma
Avoid exposure
150
# Give the unit and unit symbol for
Mass, m
kilogram (kg)
151
Give a use for visible light
Seeing, optical fibres, photography
152
What component is this?
Variable resistor
153
# What equation links;
average speed, distance and time
speed = distance ÷ time
average speed = total distance ÷ total time
154
How can you prevent heat transfer by conduction?
Use insulators (such as air)
155
Waves transfer ……………………………… without transferring ……………………….
Waves transfer energy and information without transferring matter
