GCSE Physics P2 (edexcel)

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What is the build up of static caused by?
Friction
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What's the principle of static electricity?
When 2 insulating materials are rubbed together electrons are scraped off one and dumped on the other
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What's the effect of the electric transfer caused by friction?
One material has a negative charge and one a positive
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Which way are electrons transferred during friction?
It depends on the materials involved
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Example of static electricity caused by friction?
Acetate rod and dust cloth
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3 examples of static electricity in every day situations?
Clothing crackles (caused by re-arranging charges after clothes touch hair), car shocks (clothes+seat leading to shock when touching metal), shocks from door handles (transfer of electrons form person to door)
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2 examples of charged objects attracting other objects?
Balloon sticks to the wall because balloon has a negative charge after rubbing (wall has a positive charge at the surface), negatively charged comb picks up paper (works even though paper has no charge)
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What's the name of the process where charged objects attract neutral ones?
Induction
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How is lightning caused?
Rain drops+ice rub together and give cloud positive charge at the top and negative at the bottom, creates voltage and spark
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Use of electrostatic charges?
Paint sprayers for cars and bikes
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Describe how paint sprayers work and what they do?
The spray gun is given a negative charge (so is the paint inside), paint drops repel because they've the same charge, gives fine spray of paint, object to be painted gets positive charge (gives an even coat), no paint wasted
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Describe the problem of electrostatic charges where fuel is concerned?
As fuel flows out of a pipe static can build up, leads to spark which can cause explosion at petrol station, can be solved by earthing charged objects
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How can dangerous sparks be prevented?
By connecting a charged object to the ground using a conductor (eg copper wire)
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What's the name of the method of preventing dangerous sparks?
Earthing
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How does earthing work?
Provides an easy route for the static charges to travel into the ground, no build up of static means no sparks or shocks, electrons flow from ground to object or vice versa
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Why must fuel tankers be earthed?
To prevent sparks causing large explosions
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What is electric current?
The rate of the flow of charge around a circuit
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What particle carries charge in the metal wires of a circuit?
Electrons
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Why are metals good conductors?
They have free electrons which are able to move
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What's the formula involving charge,current and time (CCT)?
Charge=current x time (and rearrangements thereafter)
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What unit is time measured in (where CCT is concerned)?
Seconds
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What unit is current measured in?
Amperes (amps)
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What unit is current measured in?
Coulombs (Q)
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What kind of current do cells and batteries supply?
Direct current
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What is direct current?
Current that keeps flowing in one direction
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What type of current is supplied by the mains?
Alternating
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What is alternating current?
Current that is constantly changing direction
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What will current not flow across a component without?
Voltage across the same component
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What's another name for voltage?
Potential difference
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What is voltage?
The driving force that pushes the current around
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What is resistance?
Anything in the circuit which slows the flow down
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What determines the size of the current?
The relative sizes of voltage and resistance
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What happens if you increase voltage?
More current will flow
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What happens if you increase resistance?
Less current will flow or more voltage will be needed to retain the current current
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What happens when an electrical charge goes through a change in potential difference?
Energy is transferred
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Where is energy supplied to the charge?
At the power source to increase voltage
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Where does the charge give up the energy given at the power source?
When it falls through any voltage drop
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What's the link between voltage and energy transfer?
Bigger the voltage change=more energy transferred
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How many joules/coulombs to a volt?
1 volt=1 joule/coulomb
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What happens to current at a junction?
It splits or re-joins
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Where must an ammeter be placed in a circuit?
In series (in-line with the component)
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Where must a voltmeter be placed in a circuit?
In parallel around the component, not around variable resistor or cell
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Describe the practical to investigate relationship between voltage, current and resistance?
Ammeter in series, voltmeter in parallel, variable resistor in series, alter variable resistor and take readings (Amps,Volts,Ohms)
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What's a fixed resistor?
Current proportional to voltage (at same temperature), flat line on graph
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What does a filament lamp curve look like?
Steady increase, resistance increases as temperature increases
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What does a diode curve look like?
Only in one quadrant, steady increase
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What's the formula for potential difference?
Potential difference=current x resistance (and rearrangements thereafter)
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What's a light dependent resistor (LDR)?
Changes resistance according to light
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What happens to resistance in an LDR in bright light?
Bright light-resistance falls
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What happens to resistance in an LDR in bright light?
Bright light-resistance falls
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What happens to resistance in an LDR in darkness?
Darkness-resistance highest
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What's a thermistor?
Temperature dependent resistor
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What happens to resistance in a thermistor when it's hot?
Hot-resistance falls
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What happens to resistance in a thermistor when it's cold?
Cold-resistance rises
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When do resistors get hot?
When an electric current passes through them
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Why do resistors get hot?
Energy transfer (electrical to heat)
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What causes the energy transfer in resistors?
Electrons colliding with ions in the lattice that makes up the resistor, gives ions more energy which is emitted as heat which increases resistance so less current
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What are the disadvantages of the heating effect on a circuit?
The circuit is less efficient, components can melt (fuses use this principle)
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What's the advantage of the heating effect on a circuit?
Used in toasters (contains coil of high resistance wire)
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What is electrical power?
The rate at which an appliance transfers energy
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Where does the energy that is transferred come from?
The current
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What's the formula for electrical power?
Electrical power=potential difference x current (and rearrangements thereafter)
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What does the energy transferred by an appliance depend on?
The current, voltage and time
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What's the formula for energy transferred?
Energy transferred=current x potential difference x time
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What is speed?
How fast you're going with no regard to direction
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What is velocity?
Speed in a stated direction
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What is displacement?
Distance in a particular direction
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What's the formula for speed?
Speed=distance/time (and rearrangements thereafter)
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What is acceleration?
How quickly velocity is changing
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What's the formula for acceleration?
Change in velocity/time taken
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In a distance time graph how can we work out speed?
Gradient
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What do downhill curves on distance time graphs mean?
It's returning to starting point
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How do you calculate acceleration from a velocity time graph?
Gradient
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What do flat sections represent on velocity time graphs?
Steady speed
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How do you work out distance from a velocity time graph?
Area under a section (velocity x time)
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What do arrows show?
The size and direction of forces
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What part of the arrow dictates force size?
The length
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Why are stationary objects stationary?
All forces in balance (gravity+reaction force)
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What's happening when there is steady horizontal velocity?
All forces are in balance (weight+reaction+thrust+drag)
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What's happening when there is steady vertical velocity?
All forces are in balance (drag+weight)
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What's happening when there is horizontal acceleration?
Unbalanced forces (thrust>drag)
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What's the relationship between the size of unbalanced force and acceleration?
The bigger the unbalanced force the greater the acceleration
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What is weight?
Force measured in newtons (N)
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What causes weight?
The pull of gravity
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What is mass?
The amount of stuff in an object
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Does mass change depending on gravity?
No
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What's the formula for weight?
Weight=mass x gravitational field strength (and rearrangements thereafter)
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What's the gravitational field strength on earth?
10 N/kg
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What's the gravitational field strength on the moon?
1.6 N/kg
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What is true of falling objects in a vacuum?
They accelerate at the same rate
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What is a vacuum?
A place that contains no matter
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What causes equal acceleration in a vacuum?
No air resistance
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What is terminal velocity?
The maximum speed something can fall
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Describe terminal velocity?
As speed increases so does air resistance, this reduces acceleration and balances forces
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What's action and reaction force?
Action force is the force exerted on an object, reaction force is the equal force exerted back by the object
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What does no resultant force mean?
No change in velocity
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What is resultant force?
The overall force acting on a body
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What is resultant force if all forces are balanced?
0
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If a resultant force is present,what is happening?
Acceleration in the direction of the resultant force
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What is a vector quantity?
Something that has magnitude and direction?
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3 examples of vector quantaties?
Force, velocity and displacement
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What is the relationship between mass and acceleration?
Bigger mass=smaller acceleration
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What's the formula for resultant force?
Force=mass x acceleration (and rearrangements thereafter)
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Describe the practical to investigate force, mass and acceleration?
trolley mass constant, vary force by changing masses on a pulley, time how long it takes to reach end of a runway, calculate velocity by measuring time taken to pass 2 lines of a certain distance
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What 2 factors affect stopping distance?
Thinking distance+braking distance
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What 2 factors affect thinking distance?
Reaction time (changed by drugs/age etc), how fast you're going
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What 4 things affect braking distance?
How fast you're going, mass of vehicle, quality of brakes, how much grip there is (affected by road surface/weather/tyres)
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What ture tread depth is essential for getting rid of water in wet conditions?
1.6mm
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Describe the practical to measure frictional force on surfaces?
Heavy block on pulley along runway, put different surfaces on runway, record mass needed to slide over surface fully
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Do you need lots of friction or little to stop?
Lots
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What's the formula for momentum?
Momentum (kg m/s)=mass x velocity (and rearrangements thereafter)
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Is momentum a vector quantity?
Yes
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What causes changes in momentum?
Force
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What happens to momentum when no forces are acting?
Nothing, momentum before=momentum after
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What's the formula for force and change in momentum?
Force=change in momentum/time
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Explain how crumple zones are a safety feature?
Increases the time taken for the car to stopExplain
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Explain how seat belts are a safety feature?
They stretch slightly and increase time taken to stop which reduces force on chest
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Explain how air bags are a safety feature?
Slow you down more gradually
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Describe the practical to investigate the affect of crumple zones?
Wrap eggs in different materials and see if they crack, collisions over a longer time reduce force so egg doesn't crack
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What happens when force moves on an object?
Energy is transferred and work is done
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What's the unit for work done and energy transferred?
Joules
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What's the formula for work done?
Work done=force x distance moved in force direction
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What is power?
The rate of doing work (J/s)
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What's the formula for power?
Power=work done/time taken (and rearrangements thereafter)
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What does one watt of power equal?
1 joule of energy transferred per second
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What is kinetic energy?
The energy of movement
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What's the formula for kinetic energy?
Kinetic energy=1/2 x mass x velocity^2
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What's the relationship between kinetic energy and work done to stop vehicle?
Kinetic energy=work done by brakes to stop vehicle=maximum braking force x braking distance
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What is gravitational potential energy (GPE)?
Energy due to height
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What's the formula for GPE?
GPE=mass x gravitational field strength x height
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When is energy useful?
When it's transferred form one form to another
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What happens when something falls?
GPE is converted to kinetic energy
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What's the relationship between kinetic energy and GPE?
Kinetic energy gained=GPE lost
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What happens every time energy is transferred from one form to another?
Some energy is lost, often as heat/sound
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Where does radioactivity come from?
Unstable radioactive isotopes undergoing nuclear decay and spitting out high energy particles or waves
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What do unstable nuclei give out while decaying?
Ionising radiation
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How do we know when an unstable nucleus is going to decay?
We don't, radioactivity is completely random
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What are the 3 types of ionising radiation?
Alpha, beta and gamma
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What's the relationship between ionising and penetrative ability?
The more ionising the radiation is, the less penetrative it is
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What are alpha particles?
Helium nuclei with 2 protons and 2 neutrons
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Describe the size, mass and speed of alpha particles?
Big, heavy and slow moving
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What charge do alpha particles have?
Strong positive
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Describe the ionising and penetrating abilities of alpha particles?
Big mass+charge makes them strongly ionising, slow speed means they slowly pass atoms and are strongly ionising, pull negative electrons out of orbit, don't penetrate far
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What are beta particles?
Electrons emitted from a nucleus
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Describe the size, mass and speed of beta particles?
Quite small, no mass and quite fast
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What charge do beta particles have?
Negative
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Describe the ionising and penetrating abilities of beta particles?
Moderately ionising and penetrate moderately, ionise by repelling other electrons from their shells (like charges)
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What are gamma rays?
A type of electromagnetic radiation
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Describe the ionising and penetrating abilities of gamma rays?
Weakly ionising, can penetrate a long way, ionise by transferring energy to electrons so they break free
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What materials are needed to stop alpha, beta and gamma?
Paper, metal and thick lead/concrete
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What is nuclear fission?
A type of nuclear reaction used to release energy from uranium or plutonium
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Describe the chain reaction that occurs in nuclear fission?
Slow moving neutron fired at uranium 235, neutron absorbed by nucleus, de-stabilizes atom and it splits into 2 lighter elements and heat is released, during split 2/3 neutrons are fired into other uranium nuclei
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Example of 2 elements uranium 235 could split into?
Krypton 91 and barium 143
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How do we turn nuclear fission into electrical power?
Heat from fission used to boil water to drive steam turbine which turns generator for electrical power
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What is used to slow down fast moving neutrons released after splitting?
Uranium rods are placed in a moderator (eg graphite), this creates a steady rate of fission
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What is used to negate the problem of excess neutrons leading to a fast growing chain reaction?
Control rods (often made of boron) absorb excess neutrons, placed in between rods and get raises'lowered into reactor
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What would happen if fission was unregulated?
Large amounts of energy would be released in a very short time, fission after fission would lead to an explosion
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What is nuclear fusion?
The joining of small atomic nuclei
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Describe nuclear fusion?
2 light nuclei collide at high speed and join to create a larger nucleus (eg hydrogen join to make helium), releases lots of energy (more than fission), doesn't leave behind much waste, plenty of hydrogen to use as fuel
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What's the problem with nuclear fusion (why aren't we using it)?
Fusion only happens at high temperatures (10 million degrees) and pressures, not at low temperature+pressure because like charges repel, it's hard to create the right conditions for fusion (no material can handle that temperature)
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Describe fusion reactors?
Hold hot hydrogen in magnetic field instead of material, there is a few experimental reactors, uses more power to fuse than fusion produces
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What is cold fusion?
Scientific theory of fusion occurring at room temperature, published 1989 by Pons and Fleischmann, reported to press, caused excitement, work not reproduced reliably, some journals refused to publish, still present day funding
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What is background radiation?
The low level radiation that's around us all the time
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Where does background radiation come form?
Radioactivity form naturally occurring unstable isotopes which are all around us, radiation from space (cosmic rays) from the sun (protected by atmosphere), human activity (eg nuclear waste)
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Is the level of background radiation constant?
No, it changes depending on where you are
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Describe the distribution of background radiation?
Certain underground rocks (eg granite) cause high levels of radioactivity if at the surface and can release radon gas (radioactive), radon trapped in houses built on radioactive rocks
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Does the radioactivity of a source stay constant?
The radioactivity of a source always decreases over time
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Why does radioactivity decrease over time?
Each time a nucleus decays (causing radioactivity) it disappears, all nuclei steadily disappear, activity decreases over time, some isotopes take a few hours, some millions of years
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What's the problem with trying to measure time taken to decay?
The activity never reaches 0 so we have to use half life
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What is half life?
Time taken for the half the undecayed nuclei to decay
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What does a short half life mean?
Activity falls quickly because lots of nuclei decay quickly
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What does a long half life mean?
Activity falls slowly because nuclei don't decay for a long time
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What is the activity of a radioactive isotope measured in?
Becquerels (Bq)
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What does 1 Bq mean?
1 decay per second
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How can becquerels be measured?
A geiger-muller (G-M) tube
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How do you calculate half life?
Work out how many half lives have passed (from given values) then solving using given time
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How do you measure half life of a source using a graph?
Find the time interval on the X axis that it takes for the value on the Y axis to half, MUST SUBTRACT BACKGROUND RADIATION
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Describe the practical to simulate radioactive decay?
24 dice represent 24 atoms, 1 roll of every dice=1 time unit (eg 1 minute, 1 hour), a six means dice is removed, roll until every dice has 'decayed', plot graph of results (time and number of dice left)
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What's a use of alpha radiation?
Fire alarms in the home, alpha source between 2 electrodes, alpha causes ionisation and a current flows, smoke absorbs current which causes sound (during fire)
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What are 2 uses of gamma rays?
Sterilize food/equipment and treat cancer
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How can gamma be used to treat cancer?
High doses of gamma kill all living cells, radiotherapy, gamma rays directed at cancerous cells, damage to normal cells minimal
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How can gamma be used to sterilize food/equipment?
Exposed to gamma which kills all microbes, irradiation,food doesn't go bad as quickly, no damage to food, used for medical equipment, need gamma source of long half life (seldom replacement)
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Describe radiation being used as a 'tracer'?
Tracers, medical tracer swallowed/injected, computer detects isotope movement, used to detect cancer, must be beta or gamma so passes out of body safely, need short half life, gamma tracers used to detect leaks in underground pipes
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Describe radiation's use as a 'thickness gauge'?
Detector detects beta radiation that passes through paper, measures consistency, when value changes paper is too thick/thin so paper rollers adjust, needs long half life
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Explain the changing attitudes towards radioactivity?
Marie curie discovered radioactive properties radium in 1898, people fascinated so used it in luminous paint +watches, by 1930's people linked early death to radium exposure, further proved by long term effects of Chernobyl (1986)
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What are 2 dangers of ionising radiation?
Tissue damage and cell mutation
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How does ionising radiation cause tissue damage?
Enters cells and collides with molecules of genetic material, causes ionisation
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How doe ionising radiation cause cell mutation?
Low dose not enough to kill cells, causes mutant cells which divide uncontrollably (which is cancer)
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Explain radiation sickness?
A lot of body cells get killed at once by radiation
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Which radiation source(s) are the most dangerous outside the body?
Beta and gamma because they can get inside delicate organs, alpha not dangerous outside body because it can't penetrate skin
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Which radiation source(s) are the most dangerous inside the body?
Alpha because damage done in a very localized area and cannot pass out of body, beta and gamma just pass out the body
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How do you protect yourself from radiation exposure in the lab?
No skin contact with source, keep source at arms length, do nto look directly at source, point source away form body, store in lead box, do not leave out
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How do you protect yourself against nuclear radiation?
Full protective suits to prevent radiation inhalation, lead suits and concrete/lead barries to protect against gamma rays, workers use robot arms to control things
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Why is nuclear waste a problem for the industry?
Fission releases lots of energy but produces products that can't be thrown away, waste product cannot be recycled, has long half life, needs to be put far way form people to do no harm
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2 ways to deal with nuclear waste?
Vitrification, melt waste with other types of material into glass and seal inside steel container then bury deep underground, pack into thick metal containers then bury waste in deep hole then fill with tonnes of concrete
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4 cons of nuclear power?
Bad public perception, nuclear waste (danger of leak or contamination), risk of leaks from power station or accidents (eg Chernobyl), high initial cost+decommissioning cost
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5 pros of nuclear pwer?
Pretty safe, very reliable (reduces reliance on fossil fuels), no co2 released, huge energy from small amount of material, uranium is cheap and readily available
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Other cards in this set

Card 2

Front

What's the principle of static electricity?

Back

When 2 insulating materials are rubbed together electrons are scraped off one and dumped on the other

Card 3

Front

What's the effect of the electric transfer caused by friction?

Back

Preview of the front of card 3

Card 4

Front

Which way are electrons transferred during friction?

Back

Preview of the front of card 4

Card 5

Front

Example of static electricity caused by friction?

Back

Preview of the front of card 5
View more cards

Comments

AmdadulHaque11

confusing when prtinting

wulrus and lucy

confusing when prtingting

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