Topic 9) Electricity & Circuits Flashcards
what is current
the flow of electrons around a circuit
what are the units for current?
amps, A
what is potential difference?
the force driving the flow of electrons around a circuit
what is another name for potential difference?
voltage
what are the units for potential difference?
volts, V
what is resistance?
everything that resists or opposes the flow of electrons in a circuit
what are the units for resistance?
ohms
which way does current flow around a circuit?
positive terminal –> negative terminal
what does a diode do?
only allow current to flow one way around a circuit
for wires and resistors, how does temperature affect resistance?
increasing the temperature will increase the resistance
why does increasing the temperature of a wire increase its resistance?
at higher temperatures, the particles in the wire vibrate faster, which slows the flow of electrons, increasing the resistance
what does a light emitting diode do?
LED will emit light when current flows through it, and only allow current to flow in one direction
what does an ammeter do?
measure the current in a circuit
where should an ammeter be placed?
in series with components
what does a voltmeter do?
measures the potential difference across a component
where should voltmeters be placed?
in parallel across the component
what is a thermistor?
a resistor whose resistance decreases as temperature increases
what is a thermistor used for?
to measure the temperature
what is a light dependent resistor?
a resistor whose resistance decreases as light intensity increases
what is a light dependent resistor used for?
to measure light intensity
what is a variable resistor?
a resistor whose resistance can easily be changed by moving a slider
what is a fixed resistor?
a resistor that has a fixed resistance that cannot be changed
what is a series circuit?
a circuit in which all the components are in the same loop
what happens to the potential difference in a series circuit?
it is shared across all the components
how do you find the total resistance of a series circuit?
add together the resistance of each component in the circuit
what happens to current in a series circuit?
current is the same for every component in a series circuit
what is the main advantage of a series circuit?
simple to set up
what is the main disadvantage of a series circuit?
if any single component breaks, the whole circuit will stop working
what is a parallel circuit?
a circuit in which each component has its own loop
how does potential difference work in a parallel circuit?
all the components in a parallel circuit have the same potential difference
what happens to current in a parallel circuit?
the total current is shared between all of the parallel loops
what happens to resistance in a parallel circuit?
the more loops you have in a parallel circuit, the lower the total resistance will be
what is the main advantage of a parallel circuit?
if one component breaks, the circuit as a whole will continue to work
what is alternating current?
a current that periodically reverses its direction
-it keeps changing its direction
what is direct current?
a current that always travels in the same direction around a circuit
what creates an alternating current?
an alternating voltage, for example from mains electricity
what creates a direct current?
a current that always travels in the same direction around a circuit
what creates an alternating current?
an alternating voltage
what creates a direct current?
a direct voltage
what is mains electricity?
the electricity generated by power stations and delivered to homes via the national grid
-wall sockets
what is the frequency of mains electricity?
50 Hz
what is the voltage of mains electricity?
230-240 volts
what is a 3 core cable?
the wire that attaches a device ti the mains supply
what are the names of the 3 wires in a plug?
live wire
neutral wire
earth wire
what is wrapped around each wire, and why?
insulated plastic, so it doesn’t conduct electricity to things it touches
what colour is the plastic wrapped around the live wire?
brown
what colour is the plastic wrapped around the neutral wire?
blue
what colour is the plastic wrapped around the earth wire?
stripes of yellow and green
what is the function of live wire?
to carry the alternating potential difference from the mains supply
what is the function of neutral wire?
to complete the circuit
what is the function of earth wire?
it is the safety wire to stop the appliance becoming live
what is the potential between the live wire and earth wire?
230 V
what is the potential difference between the neutral wire and earth wire?
0 V
which wire can be dangerous to touch?
live wire
what does surge mean and why is it dangerous?
a surge is a sudden increase in current
this can damage an appliance, and cause fire
name 4 safety mechanism that can be used in electrical circuits?
fuses
circuit breakers
earth wires
double insulation
how does a fuse work?
fuses have a thin wire which melts and blows the circuit when the current is too high
how do you decide which fuse rating to use for a given electrical circuit?
a few amps above the recommended current
how do circuit breakers work?
they act like a switch that will trip when there is a surge
they can be reset electrically
how do earth wires protect us from electric shocks?
-the earth wire is connected to the casing of the appliance
-if the live wire touches the appliance casing
-the earth wire provides an alternating pathway for electricity to flow
how does double insulation work?
where an appliance is covered in a layer of plastic, plastic doesn’t conduct electricity, even if the appliance is live
