# Physics P2

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• Created by: livwills
• Created on: 07-03-16 16:09
What is Current?
The rate of flow of charge
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What is a Series Circut?
A loop of conductors where the current is the same throughout the circut
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What is Potential Difference?
(VOLTAGE) Energy transferred per unit charge.
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What is current measured in?
Amps by an ammeter
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What is a parallel circut?
A circut which has components connected in more than one loop.
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How is current spread in a parallel circut?
The current divides at the junction but the total current in = the total current out
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What is potential difference measured in and by?
Volts- Voltmeter
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In a series circut, how is potential difference spread?
It is shared between the components
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In a parallel circut, how is potential difference spread?
The P.D across each loop is the same as the P.D from the cell (battery)
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What is electric current?
A flow of moving charges
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What happens if a component has a high resistance?
Only a small current will flow through
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What is resistance measured in?
Ohms (omega sign)
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What is the equation for resistance?
Resistance = Voltage/Current
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What was Ohms Law?
Voltage is proportional to current in some materials.
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What line on a graph do Ohmic components have?
Straight
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What material does not obey Ohms Law?
Filament light bulb (as current increases, resistance increases)
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What is a diode?
A component which only allows current to flow in one direction (forward)
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What is the resistance like in a diode?
It is very high in the opposite direction of travel
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Describe a thermistors resistance
Resistance decreases when it is heated
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What is a component with a high resistance's potential difference like compared to a component with a low resistance?
A component with a high resistance will have a larger potential difference (voltage) compared to one with a smaller resistance
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What happens to the potential difference when you add several cells together in a series circut?
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What happens to a cell connected in the opposite way to the others potential difference?
It becomes negative
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Describe the size of the current that flows through a loop with a high resistance ( Parallel)
High resistance = Small current. Low resistance = Large current
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If a loop has multiple components the potential difference is...
...shared acrosss the components
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If a loop has multiple components the current is...
...the same through each component
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What do cells and batteries produce?
Direct current flowing in one direction
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What does alternating current do?
Repeatedly changes direction
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What is the voltage for mains electricity?
230V (50Hz)
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What does an oscilliscope display?
The direct current or alternating currents voltage.
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What does the amplitude of the trace show?
The maximum potential difference supplied (in volts)
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What does the number of squares between the peaks on an oscilliscope show?
Time per cycle (in seconds)
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How do you calculate the frequency of the supplied voltage?
Frequency (Hz) = 1/time per cycle (seconds)
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What colour is the neutral wire?
Blue
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What colour is the live wire?
Brown
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What colour is the earth wire?
Green and yellow
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What does double insulated mean?
An appliance has a plastic outer case and no touchable metal parts
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What two wires do double insulated materials use?
Live and neutral
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What happens if there is a fault and the equipment goes live?
The current flows through the earth wire and blows (melts) the fuse
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What is the fuse connected in series with?
The live wire
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What does the fuse do?
It protects the appliance and flex from overheating.
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What happens if the current is too big?
The fuse melts and breaks the circut
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Why are you more likely to get an electric shock with wet skin?
Wet skin has a lower resistance compared to dry skin so electrocution is more likely
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What do RCCB's protect from?
Electrocution
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What should the current in the live and neutral wires be?
The same
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What do RCCB's do is there is a difference in current?
They break the circut in less than 0.05 seconds.
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What are fuses rated in?
Amps
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How do you calculate which fuse to use?
Use current(Amps) = Power (Watts)/ Voltage(Volts)
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What does an electric current do?
Transfers energy
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How do you calculate energy transferred?
energy transferred (J) = Power (W) x time (s)
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What is charge measured in?
Coulombs (Q)
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What is the equation for current?
Current (A) = charge (Q)/Time (s)
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How many joules of energy does one volt give to a coulomb of charge?
one
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Whta is the calculation for energy supplied?
Energy (J) = Potential difference (V) x Charge (Q)
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## Other cards in this set

### Card 2

#### Front

What is a Series Circut?

#### Back

A loop of conductors where the current is the same throughout the circut

### Card 3

#### Front

What is Potential Difference?

### Card 4

#### Front

What is current measured in?

### Card 5

#### Front

What is a parallel circut?