Physics Unit 2 Revision Cards


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where are the protons, neutrons and electrons in an atom?
the protons and neutrons lie in the nucleus, the electrons lie in outer shells
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what are the charges of these fundamental particles?
protons +1 , neutrons 0 , electrons -1
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how can an insulator be charged?
insulating materials can be given an electrostatic charge by rubbing two materials together. Electrons are transferred from one material to another giving them either a positive or negative charge
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how can the charge of a material change?
it can gain electrons, giving it a positive charge, or lose electrons, giving it a positive charge
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what do like and unlike charges do?
like charges repel, unlike charges attract
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what are some examples of common electrostatic phenomena?
shocks from everyday objects, lightning, attraction by induction such as a charged balloon attracted to a wall or a charged comb picking up a piece of paper
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what is earthing?
the removal of excess charge by movement of electrons
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what are some uses of electrostatic charge?
paint sprayers, insecticide, refuelling aircrafts
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how to paint sprayers work?
the paint nozzle is connected to an electrical supply, the droplets are given the same kind of static charge so they spread out evenly, the object being painted is given an opposite charge so the paint is attracted to the object
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how does insecticide work?
the nozzle of sprayer is connected to a mains supply, the droplets are given the same kind of static charge, these droplets repel each other so the spray spreads out evenly
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how do they refuel aircrafts?
a conducting wire (bonding line) is connected to earth any static charge on the aeroplane before refuelling starts. electrons can flow along the wire to the earth to neutralise the static charge
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what are some electrostatic dangers?
especially during refuelling aircrafts, the charge can cause sparks and these sparks can ignite causing explosions, they are earthed to prevent this build up of charge
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what is an electric current?
the rate of flow of charge
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what is the current in metals?
a flow of electrons
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what is the equation for charge?
Q = I x t
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what current do cells and batteries supply?
direct current d.c.
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what is direct current?
a movement of charge in one direction only
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where is an ammeter placed in a circuit?
in series with the circuit
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what does the ammeter measure?
current
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what does the current in the circuit depend on?
the potential difference of a source
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what happens at a junction?
current is conserved
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where is a voltmeter placed in a circuit?
in parallel
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what does a voltmeter measure?
the potential difference across it
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what is potential difference?
potential difference (voltage) is the energy transferred per unit charge passed
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what does changing the resistance do?
changes the current
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how can you change the resistance?
use a variable resistor
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what is the equation for potential difference?
V = I x R
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what does the current do in filament lamps?
it increases really quickly then slows down (r curve )
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what does the current do in diodes?
starts behind the y axis, travels along the bottom then increases once it passes the y axis
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what does the current vary with fixed resistors?
it stays constant
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What does an LDR change with?
the resistance of a light - dependent resistor changes with light intensity
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how does the resistance of a thermistor change?
the resistance of a thermistor changes with change of temperature (negative temp coefficient thermistors only)
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what happens when there is an electric current in a resistor?
there is an energy transfer which heats the resistor
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why is there an energy transfer?
because the free delocalised electrons in the lattice collide and create energy
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what is the equation for electrical power?
P = I x V
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what is the equation for energy transferred?
E = I x V x t
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what are vector quantities?
quantities that have direction as well as magnitude
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what do distance time graphs show you about speed?
the steepness of the lines show us how fast the object is going
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what is velocity?
velocity is speed in a certain direction
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what is the equation for speed?
S = D / t
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what is the equation for acceleration?
a = (v-u) / t
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what can velocity time graphs show you?
it shows acceleration of an object, you can work out the distance travelled by working out the area underneath the line
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what can free body diagrams show you?
a free body diagram represents all the forces on a single body. larger forces are shown using larger arrows
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what happens to the force when two bodies interact?
action / reaction. two touching objects exert force on eachother. the first force is the action force, the object it is hitting exerts an equal and opposite reaction
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what is the resultant force?
a resultant force is calculated using a range of forces including resistive forces, the resultant force is the effect that the forces have on an object
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what does it mean if the resultant force is zero?
the body will remain at rest or continue to move at the same velocity
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what does the acceleration, acted on by the resultant force depend on?
the size of the resultant force, the mass of the object
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what is the equation for force?
F = m x a
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what is the equation for weight?
W = m x g
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what is the acceleration in a vacuum?
all bodies accelerate at the same rate
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what is the first stage of an object falling?
air resistance increases with increasing speed
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what is the second stage of an object falling?
air resistance increases until it is equal in size to the weight of the falling object
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what is the last stage of an object falling?
when the two forces are balanced, acceleration is zero and terminal velocity is reached
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Other cards in this set

Card 2

Front

what are the charges of these fundamental particles?

Back

protons +1 , neutrons 0 , electrons -1

Card 3

Front

how can an insulator be charged?

Back

Preview of the front of card 3

Card 4

Front

how can the charge of a material change?

Back

Preview of the front of card 4

Card 5

Front

what do like and unlike charges do?

Back

Preview of the front of card 5
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