100 or so IGCSE Physics things to learn Flashcards
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
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
What happens to the resistance of a thermistor as it is heated
High temperatures reduces the resistance of a thermistor
Give the unit and unit symbol for
Power, P
watt (W)
Give the unit and unit symbol for
Density, ρ
kilogram per metre cubed (kg/m3)
What component is this?
Bulb
What does work done = energy transferred mean?
If you do 10J of work on a system you transfer 10J of energy to it.
What materials does conduction happen best in and why?
Solids; particles are close together so can pass energy quickly. Works best of all in metals due to free electrons.
What equation links;
weight, mass and gravitational field strength
weight = mass x gravitational field strength
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
How does a fuse work
When the current goes higher than the value of the fuse it melts. This breaks the circuit and stops current flowing
Give a use for x-rays
looking at the insides of things (medical imaging and other objects)
Give the unit and unit symbol for
Acceleration, a
metre per second squared (m/s/s, m/s2)
How would you find the volume of a regular object (e.g. a cube of metal)
measure each side (with ruler) and multiply together
What equation links;
pressure, force and area
pressure = force ÷ area
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
Describe a longitudinal wave and give an example
Longitudinal waves travel parallel to the oscillation which caused them. E.g. sound
Give a use for radio
Communictions and broadcast
What are the energy transfers involved with nuclear power
nuclear ⇒ thermal ⇒ kinetic ⇒ electrical
Give a danger and use for microwaves
Danger = internal heating of body tissue,
Use = cooking and satellite communications
What equation links;
charge, current and time
charge = current x time
Give a danger and use for ultra violet
Danger = blindness and damage to surface cells,
Use = flourescent lamps, security markings
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.
What happens to the current in a circuit when the resistance is decreased?
Current increases as resistance decreases
The gradient of a velocity-time graph gives
Acceleration
The gradient of a distance-time graph gives
Speed
Explain series circuits
Only one loop, simple, if one component fails no current flows
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)
The universe is made up of….
Billions of galaxies
What equation links;
acceleration, change in velocity and time taken
acceleration = change in velocity ÷ time taken
Define the time period of a wave
Time period is how long it takes for a wave to pass a point
What equation links;
work done, force and distance moved
work done = force x distance moved
What is the order of the EM spectrum
Radio, Microwave, Infra-red, Visible, Ultra-violet, X-ray & Gamma
When a wave is refracted what two things change
Speed and direction change during refraction
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.
What equation links;
moment, force and perpendicular distance from pivot
moment = force x perpendicular distance from pivot
Give the unit and unit symbol for
Charge, Q
coulomb (C)
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
Give the unit and unit symbol for
Potential Difference, V
volt (V)
What component is this?
Thermistor
What is the force which opposes motion
Friction (e.g. against a road) or drag (e.g. moving through air)
Give the unit and unit symbol for
Wavelength, λ
metre (m)
Factors which affect braking distance
Speed, weight of vehicle, quality of brakes and tryes, road surface
Give the unit and unit symbol for
Pressure, p
pascal, newton per metre (Pa, N/m2)
What equation links;
wave speed, frequency and wave length
wave speed = frequency x wave length
What are the energy transfers involved with water power
gravitational ⇒ kinetic ⇒ electric
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
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.
How does convection produce wind?
Air is heated, expands, becomes less dense, rises, colder air rushes into the area of low pressure.
What is the relationship between force and extension for a spring
Force is directly proportional to extention (if force doubles extension doubles)
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
What makes something an elastic material
Material regains original shape once stretching force is removed
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
Describe how thermal energy is transferred by radiation
Thermal radiation is an electromagnetic wave.
What is the frequency range for human hearing
20 Hz - 20 000 Hz
The initial linear part of a force-extension graph is linked to what law?
Hooke’s Law (Force is directly proportional to extension)
Our local galaxy is called
The Milky Way
What component is this?
LDR (light dependent resistor)
When the angle of incidence is greater than the critical angle light is…
Totally internally reflected
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.)
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.
Why does an object reach terminal velocity?
As the speed and drag increase, eventually weight = drag so no resultant force
Natural satellites (e.g. moons) and artificial satellites (e.g. Hubble) orbit what?
Planets
What equation links;
energy transferred and work done
energy transferred = work done
Factors which affect thinking distance
Speed, awareness (tired, alcohol)
What are the energy transfers involved with fossil fuels
chemical ⇒ thermal ⇒ kinetic ⇒ electrical
Give the unit and unit symbol for
Area, A
metre squared (m2)
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.
What equation links;
gravitational potential energy, mass, g and height
gravitational potential energy = mass x g x height
What is the principle of conservation of energy
Energy cannot be created or destroyed; only changed from one form to another.
Where does the ray go next in each case?
Give the unit and unit symbol for
Electric current, I
amp (A)
A galaxy is made up of…
Billions of stars
How would you describe a uniform field (3 marks)
Field lines are straight, parallel and equally spaced in a uniform field
Define frequency
Frequency is the number of waves going past a point per second
List the 5 types of non stored energies
Light, sound, thermal, kinetic, electrical
If a car has 20 000J of kinetic energy, how much work do the brakes have to do to stop the car?
20 000J
What is double insulation
Appliances with plastic cases are double insulated; even if live wire comes loose inside, a user can’t be shocked
What component is this?
Diode
What happens to the current in series circuit as more bulbs are added?
More bulbs in series increases the resistance and decreases the current
What are the energy transfers involved with solar cells
light ⇒ electrical
The area under a velocity-time graph gives
Distance travelled
What part of the EM spectrum has the highest frequency (and energy)
Gamma has the highest frequency
What happens to the speed of an object as it falls?
What happens to its drag?
Speed increases (resultant force downwards)
drag increases
What are the energy transfers involved with solar heating systems
thermal ⇒ themal
Describe how thermal energy is transferred by conduction
Particles knock into each other and pass on the energy
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)
How can you see the shape and direction of a magnetic field
Use plotting compasses
What equation links;
refractive index and critical angle
n = 1 ÷ sin c
refractive index = 1 ÷ sin (critical angle)
Refraction is when a wave………………………..
…bends
Name some electrical conductors (low resistance, allow current to easily flow)
Metal, graphite
Comets orbit what? What shapes are their orbits?
Comets orbit stars (e.g. the Sun) in elliptical orbits
What part of the EM spectrum has the longest wavelength
Radio has the longest wavelength
What is the law of reflection?
Angle of incidence = Angle of reflection
Define wavelength
Wavelength is the distance between two peaks or two troughs
Give the unit and unit symbol for
Moment
newton metre (Nm)
How can you increase the speed of a motor (or volume of a speaker)?
Stronger magnet, more current
Give an example of an AC source and a DC source
Mains are an AC source. Batteries are DC sources
The rate of doing work is also known as?
Power
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.
What is produced around a conductor when electrical current flows?
An electromagentic field is created when current flows
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)
Give the unit and unit symbol for
Frequency, f
hertz (Hz)
Describe how thermal energy is transferred by convection
Hotter regions of fluid expand, become less dense and float on colder regions
Give the unit and unit symbol for
Length, l
metre (m)
Where does an objects weight always act
Through its centre of gravity
List the 4 types of stored (potential) energies
Gravitational, Elastic, Nuclear, Chemical
Why is the image in a mirror virtual?
The image in a mirror can’t be projected onto a screen
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
What happens to the resistance of an LDR as more light is shone on it?
Bright light reduces the resistance of an LDR
Name some electrical insulators (high resistance, do not allow current to flow)
Plastic, wood, (pure) water
What equation links;
force, mass and acceleration
force = mass x acceleration
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
What equation links;
density, mass and volume
density = mass ÷ volume
What is the critical angle
When ligh hits the boundary at the critical angle the angle of refraction is 90°
Forces can do what to an object?
Change speed, shape or direction
What is the efficiency of this machine
useful output energy = 10J
total input energy = 100J
efficiency = 10/100
= 0.1 or 10%
How can you prevent heat transfer by radiation?
Shiny surfaces are poor emitters. They also refelect the thermal radiation back.
Define amplitude
Amplitude is the maximum displacement above the equilibrium
Give the unit and unit symbol for
Energy, E
joule (J)
Give the unit and unit symbol for
Resistance, R
ohm (Ω)
What are the energy transfers involved with wind power
kinetic ⇒ electric
Planets orbit what? What shape are their orbits?
Planets orbit stars (e.g. the Sun) in circular orbits
One Watt is equal to what?
1 watt is 1 joule per second
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
What equation links;
pressure difference, height, density and g
pressure difference = height x density x g
Reflection is when a wave…………………………
…bounces off something
Electrical hazards include….
Frayed cables, damaged sockets, water near sockets and metal objects in sockets
Give a danger and use for infra red
Danger = skin burns,
Use = cooking and night vision equipment
Give the unit and unit symbol for
Time, t
second (s)
Give the unit and unit symbol for
Volume, V
metre cubed (m3)
What are meters X and Y?
X is a voltmeter (in parallel)
Y is an ammeter (in series)
What equation links;
voltage, current and resistance
voltage = current x resistance
What equation links;
kinetic energy, mass and speed
kinetic energy = 1/2 x mass x speed2
Give a danger and use for gamma
Danger = cancer, mutation,
Use = sterilising food and medical equipment
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)
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.
What are the energy transfers involved with geothermal power
(nuclear) ⇒ thermal ⇒ kinetic ⇒ electric
How can you prevent heat transfer by convection?
Trap the fluids (e.g. trapping air in wool). This prevents both conduction and convection.
What component is this?
Wire
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
Give the unit and unit symbol for
Force, F
newton (N)
What component is this?
Diode
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
What is another name for the rate of flow of charge?
Current
Why aren’t machines 100% efficient?
Typically some energy is lost to the surroundings as heat.
Give the unit and unit symbol for
Velocity (initial, final), (u,v)
metre per second (m/s)
Give the unit and unit symbol for
Temperature, T
kelvin (K)
What is the easiest way to reduce risk of injury from microwaves, infra red, ultra violet or gamma
Avoid exposure
Give the unit and unit symbol for
Mass, m
kilogram (kg)
Give a use for visible light
Seeing, optical fibres, photography
What component is this?
Variable resistor
What equation links;
average speed, distance and time
speed = distance ÷ time
average speed = total distance ÷ total time
How can you prevent heat transfer by conduction?
Use insulators (such as air)
Waves transfer ……………………………… without transferring ……………………….
Waves transfer energy and information without transferring matter
