Physics Unit 2
Everything you will need to know for the physics unit 2 exam.
- Created by: Bethan
- Created on: 03-12-12 21:04
What is a radioisotope?
an isotope that undergoes radioactive decay, it has an unstable nucleus.
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What is ionising radiation?
radiation that is able to produce ions when it is absorbed by matter.
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What is an ion?
an element that has either given or taken away electrons from another element so it is charged.
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What are the three types of radiation?
alpha, beeta and gamma
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for the same amount of energy which type of radiation causes the most damage and which the least?
alpha causes the most and gamma the least.
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what is human exposure to ionising radiation measured in?
Sieverts (Sv)
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what are the six main applications of radioisotopes?
smoke alarm, radiotherapy for thyroid cancer, sterilisation of medical equipment, kidney scans, radioactive tracer and monitoring the thickness of materials.
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what are the three wires called in a three pin plug?
earth wire, neutral wire and the live wire
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what is the purpose of the live and neutral wire.
the live wire carries current to the appliance and the neutral wire carries current away from the appliance.
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what is newton's first law?
an object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.
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what is newton's second law?
force=mass x acceleration
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what is newton's third law?
for every action there is an equal opposite reaction.
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what is acceleration measured in?
m/s2
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what is force measured in?
newtons (N)
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how are force and motion connected?
an object will have greater acceleration if a greater force is applied to it.
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if mass remains constant doubling the acceleration does what to the force?
doubles the force.
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if force remains constant doubling the mass does what to the acceleration?
halves the acceleration
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what is velocity?
velocity is speed in a given direction.
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how do you work out the average velocity?
overall displacement / total time of travel
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how many types does charge come in and what are they called?
two types called positive and negative.
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what is positive charge carried by?
protons
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what is negative charge carried by/
electrons
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what is charge measured in?
coulombs (C)
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what is the letter used to represent charge?
Q
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how do you work out charge?
charge=current (in amps, A) x time (in seconds, S)
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what is the purpose of a cell?
transforms chemical energy into electrical energy.
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what is a battery?
two or more cells in series.
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what is the purpose of a bulb?
glows when a circuit is complete
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what is the purpose or an open switch?
the circuit is broken
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what is the purpose of a resistor?
it slows down the flow of electrons in a circuit
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what is the purpose of a light dependent resistor (LDR)?
the resistance depends on the light. more light means less resistance. In light, current will flow through the circuit.
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what is the purpose of a variable resistor?
it slows down the flow of electrons in a circuit. the resistance can be changed.
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what is the purpose of a closed switch?
it connects the components in a circuit.
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what is the purpose of a light emitting diode (LED)?
current only flows in one direction, it doesn't light up if it is the wrong way round.
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what is the purpose of a fuse?
used for cutting of an electrical current when there is an overload of electricity.
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what is the purpose of a thermistor?
the resistance depends on the temperature.
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what is the purpose of a voltmeter?
measures the voltage produced by a power supply.
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what is the purpose of a ammeter?
measures the flow of electrons in a circuit, which is known as current.
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what is current?
number of coulombs per second
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what is voltage (potential difference)?
number of joules per coloumb
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what are the three types of heat transfer?
conduction, convection and radiation
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what is an example of the discharge of static electricity?
lightning
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how does lightning work?
as the water molecules inside the cloud rub together they become charged. The charge builds up and without warning a bolt of lightening is released. The charge makes its way to earth by the easiest route.
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speed tells us what about the direction we travel in?
nothing
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what is the equation for speed?
speed=distance / time
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what is speed measured in?
m / s
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describe convection currents in air
heated less dense air rises, warm air displaces cooler air, cool dense air falls, cool air flows to fill the gap left by the rising heated air.
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what is payback time?
how long it takes for something to save the money you paid for it in the first place.
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what does cost effective mean?
how much money they save you so something that is more cost effective would save you more money annually then something that was less cost effective.
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what is resistance?
the opposition that an electrical device has to the flow of electrical current.
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what is the equation for resistance?
resistance (ohms) = potential difference (V) / current (A)
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if temperature increases does the resistance increase?
yes
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for a filament bulb reversing the voltage does what to the direction of the electric current?
reverses it
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does the filament bulb obey ohm's law?
no
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how many directions does current flow through a diode?
one
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what does the temperature of a thermistor do as the resistance decreases?
increases
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what does the resistance of a LDR do as the light intensity increases
decreases
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what do you need to do to the frictional force to travel at a steady speed?
balance it
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when does drag act?
when an object passes through a fluid.
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how do you reduce drag on an abject?
make it streamlined
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as speed increases drag also increases, true or false?
true
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the speed of an object depends on what three things?
how streamlined it is, how dense the fluid is and the strength of the bonding between particles
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do more viscous liquids have stronger or weaker bonds?
stronger
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a force (a push or a pull) causes an object to do which four things?
speed up, slow down, change direction and change shape.
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what is resultant force?
when all acting forces are replaced by a single force having the same effect as the original forces acting together
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if the resultant force is zero what effect does this have on the motion of an object?
the object's velocity stays the same
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if the resultant force is the direction the object is going what effect does this have on the motion of the object?
the object accelerates
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if the resultant force is in the opposite direction to the object what is the effect on the motion of the object?
the object decelerates
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what are the two types of current?
direct current (DC) and alternating current (AC)
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how may ways does dc current flow
one way
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is dc current negative or positive?
either
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what supplies dc current?
batteries or cells
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what does dc current show on an oscilloscope?
a flat line
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what isthe type of current in all mains electricity?
ac current
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do the electrons in ac current travel far?
no
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how do the electrons in ac current obtain their energy?
by bumping into each other
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which way does ac current travel?
one way then another, constantly changing direction
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what is the time period on an oscilloscope?
the time it takes for one complete wave
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what is kinetic energy?
movement
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what does kinetic energy depend on?
an object's mass or speed
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how do you work out kinetic energy?
kinetic energy = 1/2 x mass x velocity2
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how do you work out potential energy?
EP = M (mass) x G (gravity) x H (height)
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what is one way to work out power?
power (W,watt) = energy transferred (J,joule) / time (S,seconds)
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what is another way to work out power?
power (W) = current (A) x potential difference (V)
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what is a residual current device (RCD)
a device that disconnects a circuit when the electric current is not balanced
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how do RCDs work?
by comparing live and neutral currents and it trips out if they are different
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what do RCDs protect people from?
electric shocks
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what are RCDs not very good at protecting?
the appliance form overload
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where does nuclear radiation come form?
the nucleus of an atom
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what are alpha, beta and gamma made of?
alpha - helium nucleus, beta - electron, gamma - burst of energy
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what does alpha decay do to the atomic and mass number of an atom?
decreases mass number by 4 and decreases atomic number by 2
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what does beta decay do to the atomic and mass number of an atom?
doesn't change the mass number and increases the atomic number by 1
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what does gamma emission do to the atomic and mass number of and atom?
doesn't change the mass number and doesn't change the atomic number
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what are alpha particles completely stopped by?
a sheet of paper
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what are beta particles stopped by?
thick aluminium shielding
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what are gamma rays reduced by?
lead
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what is radioactive decay?
the spontaneous release of energy as radioactive particles
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what does radioactive decay result in?
a decrease over time of the original amount of the radioactive material
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what does every radioactive element specifically have?
a half life
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what is a half life?
the amount of time taken for a material to decrease by half
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what does nuclear fission involve?
very large nuclei splitting into smaller nuclei
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what does nuclear fusion involve?
the small nuclei joining together to produce a bigger nucleus and release energy in the process
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what can nuclear fission lead to?
other nuclei to split causing a chain reaction
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what are two isotopes commonly used as nuclear fuels
uranium - 235 and plutonium- 239
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what happens when a radioactive substance is hit by a neutron?
the nucleus splits into two smaller nuclei which are radioactive, two or three more neutrons are released and some energy is released.
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what are three disadvantages of nuclear power?
contamination of radiation, risk of terrorism and nuclear power stations are very expensive to build and maintain
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what conditions are needed for fusion to occur?
high temperature and high pressure
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what is the order of the stages of a stars life?
interstella medium, stellar nebulae, protostar, main sequence star, red giant, planetary nebula, white dwarf, giant star, red supergiant, supernova, black hole then neutron star
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what is interstella medium?
the total mass of gas and dust between stars
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what is a stellar nebulae?
a cloud of gas and dust where new stars are born
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what is a protostar?
the birth of a star caused by dense regions in a nebula collapsing due to gravity
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what is a main sequence star?
the longest most stable period of a star's life where it converts hydrogen to helium in its core, generating heat and light
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how is a red giant formed?
the core runs out of hydrogen and helium in the main sequence star and the outer layers of the star expand, cool, and become a dimmer red colour.
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when is a planetary nebula formed?
at the end of a red giant's life when the outer layers of the star start to drift off into space
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when does a white dwarf exist?
when a red giant collapses and its outer layers shed off what remains is a very hot dense star
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how is a giant star different to a main sequence star?
it is 100 times larger and 1000 times brighter
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when is a red supergiant formed?
after the hydrogen in a giant star's core has been used up they become the largest stars in the universe
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what is a supernova?
a dying star that explodes violently producing and extremely bright object that can last for months.
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when is a black hole created?
when a giant star undergoes a supernova, its an abject so dense that not even light can escape its gravity
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what is a neutron star?
the mass of a supernova core is not large enough, it forms a star made entirely of neutrons instead of a black hole
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on a distance time graph what shows the speed?
gradient
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what to flat sections on a distance time graph show?
when the object is stationary
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what do straight uphill or straight downhill sections on a distance time graph show?
the object travelling at a steady speed
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the steeper the line on a distance the graph the ........... the object is going
faster
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what do downhill sections on a distance time graph show
the object going back toward its starting point
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what do curves represent on a distance time graph?
acceleration or decelleration
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what does a steeping curve mean on a distance time graph?
the object is speeding up (increasing gradient)
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what does a leveling off curve mean on a distance time graph?
the object is slowing down (decreasing gradient)
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how do you work out the speed of an object from a distance time graph?
speed = gradient = vertical / horizontal
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what is acceleration in terms of velocity?
how quickly the velocity is changing
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what is weight caused by?
the pull of the gravitational force on an abject
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what is mass?
the amount of 'stuff' in an object
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objects fall through fluids (gas or liquid) reach ............
terminal velocity
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in air what causes things to fall at different speeds?
air resistance
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what is the stopping distance?
the sum of the thinking distance and the breaking distance
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what is the equation for work done?
work done = force x distance
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kinetic energy gained = .......................
potential energy lost
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how do you calculate power?
power = work done (or energy transferred) / time taken
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how do you calculate momentum?
momentum (kg m/s) = mass (kg) x velocity (m/s)
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what is the build up of static called?
friction
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what is the equation for current?
current = charge / time
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what is one equation for potential difference?
P.D. = work done / charge
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what is another equation for potential difference?
P.D. = current x resistance
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Other cards in this set
Card 2
Front
What is ionising radiation?
Back
radiation that is able to produce ions when it is absorbed by matter.
Card 3
Front
What is an ion?
Back
Card 4
Front
What are the three types of radiation?
Back
Card 5
Front
for the same amount of energy which type of radiation causes the most damage and which the least?
Back
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