IGCSE Physics Flashcards
1
Q
What happens when current flows through a resistor
A
When current flows through a resistor it heats up (this effect is used in kettles and toasters etc.)
2
Q
Name some electrical conductors (low resistance, allow current to easily flow)
A
Metal, graphite
3
Q
charge, current and time
A
charge = current x time
4
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.
5
Q
What is another name for the rate of flow of charge?
A
Current
6
Q
Charge, Q
A
coulomb (C)
7
Q
What is the nature of an electric current in a metal conductor?
A
A flow of negatively charged electrons flowing from the negative side of a battery or power supply
8
Q
Electric current, I
A
amp (A)
9
Q
Name some electrical insulators (high resistance, do not allow current to flow)
A
Plastic, wood, (pure) water
10
Q
What experiment can be done to demonstrate charging by friction?
A
Rub a plastic rod with a cloth, show charge on coulombmeter or repel/attract other charged things.
Rub a balloon on jumper / hair stick to wall.
11
Q
How can electrostatic charge cause a fire at a petrol station.
A
Charge builds up on car while driving
a spark when person touches car
+ fuel vapour = explosion
12
Q
Give some useful uses of electrostatic charges
A
Paint spraying,
Chimney precipitator (smoke cleaner),
Photocopier,
Ink Jet Printer
13
Q
How does a material gain a negative electrostatic charge?
A
Object gains electrons to gain a negative charge
14
Q
How can fires be prevented when refuelling aircraft (linked to electrostatic charge)
A
Attach Earthing strap (to discharge aircraft) before beginning to refuel
15
Q
How does a material gain a positive electrostatic charge?
A
Object loses electrons to gain a positive charge
16
Q
What are the benefits of using electrostatically charged spray paint
A
Paint has same charge so repels = fine mist, no clumps.
Object has opposite charge, attracts paint into corners and around the back
17
Q
When two objects with a positive electrostatic charge are close together they?
A
Repel as like charges repel
18
Q
How can electrostatic charge be used to clean smoke in a chimney?
A
Smoke particles charged by wires and attracted to charged plates
19
Q
What component is this?
A
Variable resistor
20
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
21
Q
What happens to the resistance of a thermistor as it is heated
A
High temperatures reduces the resistance of a thermistor
22
Q
Give an example of an AC source and a DC source
A
Mains are an AC source. Batteries are DC sources
23
Q
voltage, current and resistance
A
voltage = current x resistance
24
Q
What component is this?
A
Bulb
25
What happens to the current in a circuit when the resistance is decreased?
Current increases as resistance decreases
26
What happens to the current in series circuit as more bulbs are added?
More bulbs in series increases the resistance and decreases the current
27
Resistance, R
ohm ( )
28
What component is this?
Diode
29
What happens to the resistance of an LDR as more light is shone on it?
Bright light reduces the resistance of an LDR
30
What component is this?
Wire
31
What is double insulation
Appliances with plastic cases are double insulated; even if live wire comes loose inside, a user can't be shocked
32
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
33
What component is this?
Thermistor
34
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)
35
What are meters X and Y?
X is a voltmeter (in parallel)
Y is an ammeter (in series)
36
What component is this?
LDR (light dependent resistor)
37
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.
38
Potential Difference, V
volt (V)
39
Explain series circuits
Only one loop, simple, if one component fails no current flows
40
What component is this?
Diode
41
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.
42
Energy transferred per unit charge is known as?
Voltage
43
One volt is equal to one?..
One joule per coulomb
44
How does an Earth wire prevent electric shock
Large current flows to the Earth and blows fuse, breaking the circuit
45
What happens to a wire when current flows through it
Wire heats up
46
What appliances use the hearing effect of current?
Kettle, toaster, electric grill, electric heater
47
Why does a flowing current increase the temperature of a wire?
Electrons collide with lattice and transfer energy
48
Power, current, voltage?
power = current x voltage
49
What component has this I-V graph?
wire or resistor
50
What component has this I-V graph?
bulb
51
What component has this I-V graph?
diode
52
Describe how the current changes with voltage in wires/resistors
they are directly proportional (as long as temperature doesn't change)
53
Describe how the current changes with voltage in bulbs
non-linear
54
Describe how the current changes with voltage in diodes
non-linear
55
Why is current conserved at a junction?
Electrons aren't used up. Number of electrons entering a junction per second is the same as the number leaving per second.
56
If two componenets are connected in parallel what is the voltage across each one?
The same
57
If two componenets are connected in series what is the voltage across them
It depends on their resistances
58
In a series circuit is the supply voltage split across components?
Yes; voltage splits across components based on their resistances
59
In a parallel circuit is the supply voltage split across components?
No; voltage is the same across componenets
60
In a series circuit is the current the same everywhere?
Yes; current is the same everywhere
61
In a parallel circuit is the current the same everywhere?
No; current splits at junctions
62
energy transferred, charge, voltage
energy transferred = voltage x charge
63
What equation links pressure difference, height, density and g
pressure difference = height x density x g
64
What equation links density, mass and volume
density = mass / volume
65
When a gas or liquid is at rest, what can you say about the pressure?
at a given depth, pressure in a fluid at rest acts equally in all directions
66
How would you find the volume of a small irregular object (e.g. a pebble)
submerge in water. The volume of water displaced = volume of pebble
67
How would you find the volume of a regular object (e.g. a cube of metal)
measure each side (with ruler) and multiply together
68
What happens to the pressure acting in a fluid as you go deeper?
pressure increases as you go deeper into a fluid
69
What equation links pressure, force and area
pressure = force / area
70
How is electricity generated in a generator?
A large coil is spun in a strong magentic field, this causes a force on the electrons and makes them flow producing a current.
71
How can you increase the amount of voltage which is induced when moving a magnet into a coil?
Stronger magnet, move magnet faster
72
When a wire is moved through a magnetic field what happens?
A wire moving through a magnet causes a current to flow
73
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.
74
How can you increase the speed of a motor (or volume of a speaker)?
Stronger magnet, more current
75
How can you produce more electricity in a generator?
Stronger magnet, spin coil faster
76
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
77
What is felt when a current-carrying wire is in a magnetic field?
A force is felt when a wire carries a current in a magnetic field
78
What is produced around a conductor when electrical current flows?
An electromagentic field is created when current flows
79
A charged partical experience no force due to a magnetic field when?
Moving parallel to field
80
What force is felt by the charged particle
No force felt as particle is moving parallel to field.
81
How are electromagnets made?
A coil of wire around an iron core
82
Describe how thermal energy is transferred by conduction
Particles knock into each other and pass on the energy
83
Describe how thermal energy is transferred by convection
Hotter regions of fluid expand, become less dense and float on colder regions
84
Describe how thermal energy is transferred by radiation
Thermal radiation is an electromagnetic wave.
85
How can you prevent heat transfer by conduction?
Use insulators (such as air)
86
How can you prevent heat transfer by convection?
Trap the fluids (e.g. trapping air in wool). This prevents both conduction and convection.
87
How can you prevent heat transfer by radiation?
Shiny surfaces are poor emitters. They also refelect the thermal radiation back.
88
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.
89
How does convection produce wind?
Air is heated, expands, becomes less dense, rises, colder air rushes into the area of low pressure.
90
What are the advantages of fossil fuels?
Reliable (not weather dependent),
already established,
high power output
91
What are the advantages of geothermal power?
Renewable,
no air pollution,
low running costs, no fuel costs
92
What are the advantages of hydroelectric power?
Renewable,
no air pollution,
low running costs, no fuel costs
93
What are the advantages of nuclear power?
Reliable (not weather dependent),
already established,
high power output
94
What are the advantages of solar cells?
Renewable,
no air pollution,
low running costs, no fuel costs
95
What are the advantages of solar heating systems?
Renewable,
no air pollution,
low running costs, no fuel costs
96
What are the advantages of wind power?
Renewable,
no air pollution,
low running costs, no fuel costs
97
What are the disadvantages of fossil fuels?
Release CO2 and air pollution, mining hazardous
98
What are the disadvantages of geothermal power?
Only works in very specific places,
deep drilling difficult and expensive
99
What are the disadvantages of hydroelectric power?
Floods a large area,
disrupts people and animals
100
What are the disadvantages of nuclear power?
Produces long lasting radioactive waste which must be securely stored,
mining hazardous
101
What are the disadvantages of solar cells?
Unreliable (doesn't work at night or when cloudy),
large area needed to replace a typical power station,
inefficient
102
What are the disadvantages of solar heating systems?
Unreliable (doesn't work at night),
may need additional boiler to produce hot water
103
What are the disadvantages of wind power?
Unreliable (only works when windy),
needs lots of land,
visual pollution, a large number needed to replace a typical power station
104
What are the general advantages of renewable sources of power?
Renewable,
no air pollution,
low running costs, no fuel costs
105
What are the general disadvantages of renewable sources of power?
Unreliable (weather dependent),
large amount of land needed to replace a typical power station
106
What is the efficiency of this machine
useful output energy = 10J
total input energy = 100J
efficiency = 10/100
= 0.1 or 10%
107
What is the principle of conservation of energy
Energy cannot be created or destroyed; only changed from one form to another.
108
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
109
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.
110
Why aren't machines 100% efficient?
Typically some energy is lost to the surroundings as heat.
111
Energy, E
joule (J)
112
List the 8 energy stores
chemical, electrical, kinetic, gravitational, elastic, thermal, magnetic, electrostatic, nuclear
113
List the 4 energy transfers
mechanically, electrically, by heating, by radiation (light and sound)
114
When will an object emit thermal radiation?
When it is hotter than its surroundings
115
When will an object absorb thermal radiation?
When it is hotter than its surroundings
116
What surface is the best absorbers of thermal radiation?
Matt Black
117
What surface is the best emitters of thermal radiation?
Matt Black
118
What surface is the worst absorbers of thermal radiation?
Shiny Silver
119
What surface is the worst emitter of radiation?
Shiny Silver
120
Forces can do what to an object?
Change speed, shape or direction
121
weight, mass and gravitational field strength
weight = mass x gravitational field strength
122
Force, F
newton (N)
123
What is the force which opposes motion
Friction (e.g. against a road) or drag (e.g. moving through air)
124
force, mass and acceleration
force = mass x acceleration
125
What is the difference between scalar and vector quantities?
Vectors have a direction as well as a magnitude (size)
126
Name some vector quantities
Velocity,
displacement,
acceleration,
force,
momentum,
moment,
current
127
Name some scalar quantities
Speed,
mass,
volume,
time,
energy,
charge,
pressure,
power
128
Where does an objects weight always act
Through its centre of gravity
129
Factors which affect thinking distance
Speed, awareness (tired, alcohol)
130
What makes something an elastic material
Material regains original shape once stretching force is removed
131
Moment
newton metre (Nm)
132
What is the relationship between force and extension for a spring
Force is directly proportional to extention (if force doubles extension doubles)
133
What happens to the speed of an object as it falls?
What happens to its drag?
Speed increases (resultant force downwards)
drag increases
134
Factors which affect braking distance
Speed, weight of vehicle, quality of brakes and tryes, road surface
135
moment, force and perpendicular distance from pivot
moment = force x perpendicular distance from pivot
136
Why does an object reach terminal velocity?
As the speed and drag increase, eventually weight = drag so no resultant force
137
Which support provides more force? Why?
Moments about the person are equal.
A closer to person, so needs bigger force to provide same moment as B.
138
The initial linear part of a force-extension graph is linked to what law?
Hooke's Law (Force is directly proportional to extension)
139
How can you gain accurate results when investigating force and extension of a helical spring
Take eye level readings, keep ruler vertical and close to spring
140
How do you calculate stopping distance?
Stopping distance = Thinking distance + Braking distance
141
Force, mass, acceleration
force = mass x acceleration
142
Weight, mass, gravitational field strength
weight = mass x g
143
What force is needed in the equation F = ma?
Resultant or overall force.
144
Which direction does friction always act?
In the opposite direction to motion
145
What's wrong with -50K as a temperature?
You can't have negative kelvin temperatures, absolute zero (0K) is the coldest temperature possible
146
How do gas particles exert pressure on a container
molecules collide with walls of container,
exert a force,
over a given area,
pressure = force / area
147
Temperature, T
kelvin (K)
148
How do you convert from K to C?
What is 300K in C?
What is 100K in C?
Subtract 273,
300K-273 = 27 C,
100K-273 = -173 C
149
How do you convert from C to K?
What is 20 C in K?
What is -40 C in K?
Add 273,
20 C + 273 = 293 K,
-40 C + 273 = 233 K
150
When investigating the relationship between pressure and volume what two quatities must you keep constant?
Temperature and mass of gas must be kept constant when investigating pressure and volume
151
What happens to the pressure of a gas in a sealed container when you heat it? Why?
Pressure increases when you heat a sealed container of gas,
molecules move faster hitting walls harder and more often,
more force exerted on same area,
pressure increases
152
How can air molecules move heavy smoke particles (Brownian motion)
lots of tiny, fast moving air molecules exert enough force on a smoke particle to change its direction
153
What happens to particles at absolute zero? What is the pressure? Why?
Paricles stop moving at absolute zero (no KE), pressure is zero as particles are not colliding with walls
154
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
155
If you double the volume of a sealed container of gas (at a constant temperature) what happens to the presure?
Pressure will halve
156
If the kelvin temperature of a gas doubles, what happens to the pressure it exerts?
Pressure doubles too
157
What is the relationship between kelvin temperature of a gas and average kinetic energy its molecules?
Kelvin temperature is directly proportional to average kinetic energy.
Doubling the temperature (in kelvin!) doubles KE
158
When a magnet moves through a coil of wire what happens?
A magnet moving through a coil causes a current to flow
159
What is the relationship between input and output power of a transformer?
Pprimary = Psecondary
IpVp = IsVs
160
Why is iron used as the core for a transformer?
Soft magnetic material; gains and loses magnetism easily.
161
Why is the iron core in a transformer laminated?
Prevents eddy currents;
stops heating;
keeps efficiency high.
162
What sort of electricity is needed to make transformers work?
AC; current must change direction so magnetic field keeps changing direction
163
More turns on the secondary coil is what sort of transformer?
Step up; voltage is bigger across the secondary coil
164
Why are step up and step down transformers used in the National Grid?
Voltage stepped up (e.g 100x);
Current drops by the same amount (100x lower);
less power loss due to heating;
Stepped down to be safe in homes.
165
Why doesn't DC work for transformers?
DC doesn't change direction so the magnetic field is constant
166
More turns on the primary coil what sort of transformer?
Step down; voltage is bigger across the primary coil
167
Why is a current induced in the secondary coil?
The secondary coil sees a changing magnetic field;
electrons experience a force and move;
which induces a current
168
Describe the structure of a transformer
Two coils of wire wrapped around a laminated iron core
169
Why is the image in a mirror virtual?
The image in a mirror can't be projected onto a screen
170
When a wave is refracted what two things change
Speed and direction change during refraction
171
When the angle of incidence is greater than the critical angle light is
Totally internally reflected
172
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
173
refractive index and critical angle
n = 1 / sin c
refractive index = 1 / sin (critical angle)
174
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
175
refractive index, angle of incidence, angle or refraction
n = sin i / sin r
refractive index = sin (angle of incidence) / sin (angle of refraction)
176
What is the frequency range for human hearing
20 Hz - 20 000 Hz
177
What is the critical angle
When ligh hits the boundary at the critical angle the angle of refraction is 90
178
What is the law of reflection?
Angle of incidence = Angle of reflection
179
The frequency of a sound wave is linked to its?.
pitch
180
The amlitude of a sound wave is linked to its?.
volume
181
How can you find the frequency of a sound wave from an oscilloscope trace
Measure time period T (of one wave)
Use f = 1/T (careful with milli seconds)
e.g T = 3ms
so f = 1/0.003 = 333Hz
182
What two pieces of equipment are needed to display a sound wave?
Microphone and oscilloscope
183
Give some uses for total internal refelction
Fibre optic cables, reflectors, binoculors
184
The loundness of a sound wave is linked to its?
Amplitude
185
What is a magnetic field line?
A magnetic field line shows the direction of a magnetic field (N to S). Where lines are close together the field is strong.
186
How would you describe a uniform field (3 marks)
Field lines are straight, parallel and equally spaced in a uniform field
187
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.
188
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
189
How can you see the shape **and** direction of a magnetic field
Use plotting compasses
190
Magnets can attract?
Magnetic materials (and other magnets too)
191
Magnets can attract or repel?
Other magnets
192
What has the following magnetic field shape?
Field around a current carrying wire
193
What has the following magnetic field shape?
Field around a flat coil
| (looks like an owl)
194
Magnetically hard materials....
Are difficult to magnetise but keep their magnetism
195
Magnetically soft materials...
Are easy to magnetise but lose their magnetism quickly
196
What has the following magnetic field shape?
Field around a solenoid (same shape as a bar magnet)
197
How can magnetism be induced in a magnetic material?
Placing a magnet close to a magnetic material will induce magnetism in the magnetic material
198
What is conservation of momentum?
Momentum before a collision (or explosion) is equal to the momentum after.
Assuming no external forces act.
199
How does bending you knees help prevent injury?
Increases collision time,
lower deceleration (a=V/t),
lower force (F=ma)
200
What is Newton's third law?
If object A exerts a force on object B, object B exerts an equal and opposite force on object A
201
How does a stretching seatbelt reduce injury
Increases collision time,
lower deceleration (a=V/t),
lower force (F=ma)
202
What equation links momentum, mass and velocity?
Momentum = mass x velocity
203
The gradient of a velocity-time graph gives
Acceleration
204
The area under a velocity-time graph gives
Distance travelled
205
average speed, distance and time
speed = distance / time
average speed = total distance / total time
206
?霘The gradient of a distance-time graph gives
Speed
207
acceleration, change in velocity and time taken
acceleration = change in velocity / time taken
208
Time, t
second (s)
209
Velocity (initial, final), (u,v)
metre per second (m/s)
210
Acceleration, a
metre per second squared (m/s/s, m/s2)
211
How many alpha-particles take this path?
What does this show?
Some of the particles take this path.
It shows there is a charged region
212
What type of radioactive decay is most penetrating?
Gamma
213
What are the artificial sources of background radiation?
Medical sources, fallout from nuclear weapons testing and use, nuclear accidents
214
What are the dangers of ionising radiation?
Mutation and damage to cells and tissues
215
After two half-lives, how much of an original sample is left?
One quarter
216
What type of radioactive decay is most ionising?
Alpha
217
In what two ways can radioactive decay be detected?
By photographic film and by a Geiger-M/泓ler (GM) Tube
218
What isotope Carbon-14 often used for
radiometric dating; identifying how old something is based on the count rate of the carbon-14
219
After three half-lives, how much of an original sample is left?
One eighth
220
After four half-lives, how much of an original sample is left?
One sixteenth
221
How many alpha-particles take this path?
What does this show?
Very few alpha particles take this path.
It shows there is a central positivley charged region which is very tiny and very dense.
222
What are the natural sources of background radiation?
Radon gas, cosmic rays, the ground, food and drink
223
What is the role of the control rods in a nuclear reactor?
To control the rate of reaction by absorbing neutrons
224
What type of radioactive decay emits a helium nucleus?
Alpha
225
What types of radioactive decay do not change an isotope's mass number?
Beta and Gamma
226
Give a danger and use for gamma
Danger = cancer, mutation,
Use = sterilising food and medical equipment
227
What particle was fired at gold foil during Rutherford's experiments. What charge did it have?
Alpha particle which has a positive charge
228
What type of radioactive decay emits an electron?
Beta
229
What is the role of the moderator in a nuclear reactor?
To slow neutrons down so that they can cause new fissions
230
What type of radioactive decay changes both an isotope's mass number and its atomic number?
Alpha
231
What type of radioactive decay does not emit a particle?
Gamma
232
What is the mass number?
The total number of protons and neutrons
233
How many alpha-particles take this path?
What does this show?
Most alpha particles take this path.
It shows most of the atom is empty space
234
Do isotopes have the same atomic number, or the same mass number?
Atomic number (number of protons)
235
What type of radioactive decay can be stopped by a sheet of paper?
Alpha
236
What is the atomic number?
The number of protons
237
What type of radioactive decay can only be stopped by a few millimetres of aluminium?
Beta
238
Radioactive activity, A
becquerel (Bq)
239
What type of radioactive decay can only be stopped by a few centimetres of lead?
Gamma
240
What particle do control rods absorb?
Neutrons
241
What type of radioactive decay can be stopped by a few centimetres of air?
Alpha
242
Describe the motion of gas particles
gas particles move in a random fast motion
243
Describe the arrangement and motion of particles in a gas
No pattern;
Able to move freely/fast;
Larger space between particles;
244
Describe the arrangement and motion of particles in a liquid
Irregular pattern;
Able to move over/past other particles;
Little space between particles;
245
What change of state happens during condensing?
gas to liquid
246
What change of state happens during melting?
solid to liquid
247
What change of state happens during boiling?
liquid to gas
248
What change of state happens during freezing?
liquid to solid
249
Describe the arrangement and motion of particles in a solid
Regular pattern OR close packed;
Vibration in position;
Little space between particles
250
Comets orbit what? What shapes are their orbits?
Comets orbit stars (e.g. the Sun) in elliptical orbits
251
Our local galaxy is called
The Milky Way
252
Natural satellites (e.g. moons) and artificial satellites (e.g. Hubble) orbit what?
Planets
253
A galaxy is made up of
Billions of stars
254
Why do different planets have different values of g (gravitational field strength)
Planets with more mass (e.g. Jupiter) have a higher value of g
255
The universe is made up of .
Billions of galaxies
256
Planets orbit what? What shape are their orbits?
Planets orbit stars (e.g. the Sun) in circular orbits
257
Define amplitude
Amplitude is the maximum displacement above the equilibrium
258
wave speed, frequency and wave length
wave speed = frequency x wave length
259
What part of the EM spectrum has the longest wavelength
Radio has the longest wavelength
260
Define the time period of a wave
Time period is how long it takes for a wave to pass a point
261
Wavelength,
metre (m)
262
Waves transfer without transferring .
Waves transfer energy and information without transferring matter
263
Frequency, f
hertz (Hz)
264
What is the easiest way to reduce risk of injury from microwaves, infra red, ultra violet or gamma
Avoid exposure
265
Give a danger and use for microwaves
Danger = internal heating of body tissue,
Use = cooking and satellite communications
266
Refraction is when a wave
...bends
267
What is the order of the EM spectrum
Radio, Microwave, Infra-red, Visible, Ultra-violet, X-ray & Gamma
268
Reflection is when a wave
...bounces off something
269
Give a use for x-rays
looking at the insides of things (medical imaging and other objects)
270
Give a danger and use for infra red
Danger = skin burns,
Use = cooking and night vision equipment
271
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
272
What part of the EM spectrum has the highest frequency (and energy)
Gamma has the highest frequency
273
Give a danger and use for ultra violet
Danger = blindness and damage to surface cells,
Use = flourescent lamps, security markings
274
Give a use for visible light
Seeing, optical fibres, photography
275
Define wavelength
Wavelength is the distance between two peaks or two troughs
276
Describe a longitudinal wave and give an example
Longitudinal waves travel parallel to the oscillation which caused them. E.g. sound
277
Give a use for radio
Communictions and broadcast
278
Define frequency
Frequency is the number of waves going past a point per second
279
What is the Doppler Effect?
A change in the observed frequency of an object moving towards or away from you.
280
What happens to the observed frequency of a wave when its source is moving towards you?
Obsereved frequency increases
281
What happens to the observed wave length of a wave when its source is moving towards you?
Obsereved frequency decreases
282
What happens to the observed frequency of a wave when its source is moving away from you?
Observed wavelength decreases
283
What happens to the observed wavelength of a wave when its source is moving away from you?
Observed wavelength increases
284
Power, P
watt (W)
285
What does work done = energy transferred mean?
If you do 10J of work on a system you transfer 10J of energy to it.
286
The rate of doing work is also known as?
Power
287
If a car has 20 000J of kinetic energy, how much work do the brakes have to do to stop the car?
20 000J
288
efficiency, useful energy output and total energy input
efficiency = useful energy output / total energy input
(also efficiency = useful energy output / total energy output)
289
gravitational potential energy, mass, g and height
gravitational potential energy = mass x g x height
290
work done, force and distance moved
work done = force x distance moved
291
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)
292
One Watt is equal to what?
1 watt is 1 joule per second
293
energy transferred and work done
energy transferred = work done
294
kinetic energy, mass and speed
kinetic energy = 1/2 x mass x speed2
295
List the 4 types of stored (potential) energies
Gravitational, Elastic, Nuclear, Chemical
296
List the 5 types of non stored energies
Light, sound, thermal, kinetic, electrical
297
What are the energy transfers involved with fossil fuels
chemical ?? thermal ?? kinetic ?? electrical
298
What are the energy transfers involved with geothermal power
(nuclear) ?? thermal ?? kinetic ?? electric
299
What are the energy transfers involved with nuclear power
nuclear ?? thermal ?? kinetic ?? electrical
300
What are the energy transfers involved with solar cells
light ?? electrical
301
What are the energy transfers involved with solar heating systems
thermal → themal
302
What are the energy transfers involved with water power
gravitational ?? kinetic ?? electric
303
What are the energy transfers involved with wind power
kinetic ?? electric
