Physics paper 2

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What is mechanical energy transfers?
when a force is doing work
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What is electrical energy transfer?
when moving charges do work
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When a system changes...
energy is transferred (some is dissipated)
3 of 62
What is a closed system?
is a system in which the net change in energy is zero
4 of 62
When a force moves an object through a distance...
work is done on the object and energy is transferred
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What is power?
the rate of energy transfer
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What is the formula for power?
work done / time taken
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What is a force?
a force is a push or a pull on an object that is caused by it interacting with something
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What are non-contact forces caused by?
interacting fields
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What do interactive magnetic fields cause?
attraction or repulsion between magnetic objects
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What is the resultant force of objects in equilibrium?
zero
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How do you know if an object is in equalibrium?
all the forces are balanced and there is a resultant force of zero
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What is a moment?
a turning effect of a force
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What is the equation for moments?
moment = force x distance
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What does the principal of moments state?
That for an object in equilibrium the sum of clockwise moments = the sum of anticlockwise moments
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How do levers make it easier to do work?
they increase the distance from the pivot meaning a smaller force is needed to give the same moment
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What are gears?
circular cogs with 'teeth' around their edge
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Why are gears used?
to transmit the rotational effect of a force from one place to another
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What is the current?
the rate flow of charge
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Current will only flow through an electrical component if...
there is a potential difference across the component, and if it is a closed circuit
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What is potential difference?
is the energy transferred per coulomb of charge that passes through two points in an electrical circuit
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What is resistance?
anything that slows the flow of charge down
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The higher the potential difference across the component...
the higher the current will be
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What is the equation for charge?
charge = current x time
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What is charge measured in?
coulombs
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What is the equation for energy transferred?
charge moved x potential difference
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What is 1V?
one joule per unit coulomb
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What is the equation for potential difference?
current x resistance
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What happens when a charge flows through a component?
it has to do work against resistance
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Current will only flow through a diode...
in one direction, the diode has a very high resistance in the opposite direction
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For linear components the resistance of the component equals the...
inverse of the gradient, the steeper the graph the lower the resistance
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For an LDR, in bright light what happens to the resistance?
it falls
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For an LDR, in darkness what happens to the resistance?
it is at its highest
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For a thermistor, if the temperature increases then what happens to the resistance?
it decreases
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For a battery the what does the longer line represent?
the positive end
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What are the disadvantages of series circuits?
if one component breaks they all stop working, you can't individually control them
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How is the current distributed in a series circuit?
it is the same everywhere
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How is the potential difference distributed in a series circuit?
it is shared between components, based on their resistance
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In a series circuit what happens when you add more resistors?
the total resistance increases
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What are the advantages of parallel circuits?
if one stops working the other stay working, independant control
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In a parallel circuit how it the potential difference distributed?
it is the same across all components
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In a parallel circuit how is the current distributed?
it is shared between branches
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What happens when you add another resistor to a parallel circuit?
the total resistance decreases
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What is the equation for energy transferred in circuits?
E = current x potential difference x time
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What do fuses do?
they melt and break the circuit if the current gets too high
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What is the equation for electrical power?
power = current x potential difference
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What is the alternate equation for electrical power if you don't know the potential difference?
power = current x resistance (squared)
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What is an alternating current?
a current which is constantly changing
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How are alternating currents produced?
they are produced by alternating potential differences
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What is the UK main supple?
230 V a.c.
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What is the frequency of the mains supply?
50 Hz
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What typed of current is used in cells and batteries?
direct current
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How can you turn a.c. into d.c.?
using a diode
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What do each of the three wires in electrical supplies have inside them?
a core of copper
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What colour is the neutral wire?
blue, always at 0V and completes the circuit
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What colour is the earth wire?
green and yellow
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What does the earth wire do?
it carries the current away if something goes wrong and stops the appliance casing becoming live
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What colour is the live wire?
brown, carries the voltage
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What is included in electrical appliances to prevent shocks and fires?
the earth wire and a fuse
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Why are circuit breakers more useful than fuses?
they turn off quicker than the fuse melts, they can be reset
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An earthed conductor...
can never become live
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What are known as two core cables?
cables that only carry a neutral wire and a live wire
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Other cards in this set

Card 2

Front

What is electrical energy transfer?

Back

when moving charges do work

Card 3

Front

When a system changes...

Back

Preview of the front of card 3

Card 4

Front

What is a closed system?

Back

Preview of the front of card 4

Card 5

Front

When a force moves an object through a distance...

Back

Preview of the front of card 5
View more cards

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