P6 Electric Circuits Flashcards
What is a series circuit?
A series circuit is an unbranched loop
where the same charge passes through
all components, so the current through
each component is the same.
What is a parallel circuit?
A circuit in which the charge is split
between branches.
Describe the current across a series
circuit
The current is the same across all points
in a series circuit
Describe potential difference in a series
circuit
Potential difference is split between
components, according to the ratio of
their resistances.
Describe current across a parallel circuit
The current is divided between the
branches of the circuit
Describe potential difference across a
parallel circuit
Each branch has a potential difference
equal to the potential difference of the
supply
What is total resistance in a series
circuit?
The sum of the resistances from each
component.
What is the total resistance in a parallel
circuit?
The total resistance is lower than that of
the branch with the lowest resistance.
This is because the charge is split;
decreasing the charge to each
component decreases its resistance.
Why is it advantageous to connect lamps
in parallel?
If one lamp blows, the rest will be
unaffected and can still receive current
(i.e. the circuit is still complete).
How do multiple power sources affect
emf?
In series, the emfs of individual sources
are added to give the total emf.
Emfs in parallel do not add
What is a thermistor?
A resistor in which resistance decreases
as temperature increases.
What is an LDR?
A resistor in which resistance decreases
as light intensity increases
What is a diode?
A component which only allows current
to flow in one direction (as the resistance
in the other direction is too high).
What can diodes be used for?
As rectifiers, to convert AC into DC.
How is damaged insulation a hazard?
Sections of wire can be left exposed, and
contact can result in electric shocks or
pose a fire hazard.
How does overheating occur?
High currents cause the wires to heat up,
melting the insulation and potentially
causing a fire.
How do damp conditions pose a hazard?
Water can conduct a current, causing
electric shocks etc.
What is a fuse?
A thin piece of wire which overheats and
melts if the current is too high.
How should the rating of a fuse be
chosen?
It should be slightly higher than the
current used by the device in the circuit.
(common examples: 3A, 5A, 13A)
What is a circuit breaker?
An automatic electromagnetic switch
which breaks the circuit if the current is
above a set value.
What are advantages of circuit breakers
over fuses?
● They can be reset and used again
● They operate faster
What is an earthing wire?
A wire which creates a safe route for
current to flow down to the ground if a
short circuit is produced, preventing
electric shocks.
How do earth wires deal with surges?
They have a very low resistance, so in
surges a lot of current flows through
them, blowing the fuse and
disconnecting the circuit.
