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Physics Paper 2
Topic 10: Electricity and circuits
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Cards (34)
What is the structure of the atom?
Positively
charged nucleus with
negatively
charged electrons
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What are the subatomic particles and their charges?
Proton
: +1 charge,
mass
1
Neutron
: 0 charge, mass 1
Electron
: -1 charge, mass
0.0005
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What is a series circuit?
A closed circuit where
current
is the same everywhere
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What is a parallel circuit?
A
branched circuit
where
current
splits into multiple paths
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What does potential difference represent?
Energy transferred
per unit charge
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How is potential difference measured?
With a
voltmeter
placed in parallel across a
component
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What happens when there is a potential difference in a closed circuit?
Current
will always flow
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What is the formula for energy transferred?
E
= QV
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What is the unit of current?
Amps
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How is current defined?
Rate of flow of
charge
(
electrons
)
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How is current measured?
With an
ammeter
placed in
series
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What happens to current with greater resistance?
Current
decreases
as
resistance
increases
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What is a variable resistor used for?
To change the amount of
resistance
in a circuit
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What are the characteristics of series circuits?
Components connected end to end
Current flows through all components
Potential difference
is shared across the circuit
Total resistance is the sum of individual
resistances
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What are the characteristics of parallel circuits?
Components connected separately to the power supply
Current flows through each component separately
Potential difference is the same across all branches
Total resistance is less than the smallest branch resistance
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What is the formula for total resistance in series?
R<sub>T</sub>
=
R<sub>1</sub>
+
R<sub>2</sub>
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Why does resistance increase with length?
Longer length means more
atoms
for electrons to pass
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How does cross-sectional area affect resistance?
Thinner
wires give greater resistance
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What happens to resistance in an LDR with increased light intensity?
Resistance
decreases
with
greater
light intensity
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What is the function of a diode?
Allows
current
to flow in one
direction
only
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What is the relationship between power, current, and voltage?
Power
is
directly
proportional
to
current
and
voltage
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What is the formula for electrical power?
P
=
IV
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What is the difference between AC and DC?
AC varies continuously, DC flows in one
direction
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What is the mains supply voltage in the UK?
230V
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What color is the live wire in a plug?
Brown
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What is the purpose of the earth wire?
To prevent appliances from becoming
live
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What happens if the live wire touches the metal casing?
The appliance becomes live, risking
electric shock
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What does a fuse do?
Melts to break the
circuit
if
current
is too high
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What is power rating?
Power of the
appliance
when in use
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What are the testing relationships for varied wire resistance?
Use wires with resistance from 10 to 300
ohms
Connect to
DC voltage sources
(
2V
to
30V
)
Measure current for each voltage
Plot graph of
potential difference
against current
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What are the testing relationships for filament lamps?
Connect to
DC voltage
sources (
2V
to
12V
)
Measure current for each voltage
Plot graph of potential difference against current
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What are the testing relationships for diodes?
Connect to
DC voltage sources
(1V to 12V)
Measure
current
for each voltage
Reverse connection to measure
negative potential differences
Plot graph for
positive and negative potential differences
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What are the testing relationships for LDRs?
Use constant voltage of
12V
Measure current at varying
light intensities
Plot graph of resistance against light intensity
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What are the testing relationships for thermistors?
Use constant voltage of
12V
Measure current at varying
temperatures
Plot graph of resistance against temperature
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