electricity (p1) Flashcards
What is the circuit symbol for a bulb?
Circle with a cross
What is the circuit symbol for a cell?
Two lines, one shorter than the other
What is the circuit symbol for a battery?
Two lines, one shorter than the other, repeated at least twice
What is the circuit symbol for an ammeter?
Circle with an A
What is the circuit symbol for a voltmeter?
circle with a V
What is the circuit symbol for a switch?
break in the wire line
What is the circuit symbol for a fuse/resistor?
Rectangle with a line through
What is the circuit symbol for a diode?
Circle with an arrow and line inside
What is the circuit symbol for a LED?
Circle with an arrow and line inside and two arrows pointing out
What is the circuit symbol for a resistor?
rectangle
What is the circuit symbol for a variable resistor?
Rectangle with an arrow through
What is the circuit symbol for a thermistor?
Rectangle with a bent line through
What is the circuit symbol for an LDR?
Rectangle with a circle around and two arrows pointing in
What is the function of an electrical cell?
Provides energy to the electrons, or provides potential difference
What is the function of a battery?
Provides energy to the electrons, or provides potential difference
What is the function of a fuse?
Breaks and stops the circuit if the current is too high
What is the function of a switch?
Breaks or completes the circuit
What charge do electrons have?
negative
What equation links current, charge flow & time?
charge flow = current Γ time
What is the unit for charge flow?
Coulombs, or C
What is the unit for current?
Amps, or A
What is the unit for time?
seconds
What happens to current flow if the resistance increases?
decreased
What is the unit for potential difference?
volts
What is the unit for resistance?
Ohms, or Ξ©
What is the function of an ammeter?
Measures the current in a circuit
What is the function of a voltmeter?
Measures the potential difference through a component
Where should an ammeter be placed in a circuit?
Ammeters should be placed in series with the components
Where should a voltmeter be placed in a circuit?
Voltmeters should be placed on a parallel bridge around the component of interest
What is the function of a resistor?
Increases the resistance of a circuit
What is the function of a variable resistor?
Increases the resistance of a circuit, and can be changed
What is an ohmic conductor?
The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor.
This means that the resistance remains constant as the current changes.
What does the current-potential difference graph for an ohmic conductor (like a resistor) look like?
A straight line through 0,0
What does the current-potential difference graph for a filament bulb look like?
A curved line through 0,0
What is the function of a bulb?
Produces light radiation
What does the current-potential difference graph for a diode look like?
A curved line that increases significantly after a certain potential difference
What is the function of a diode?
Allows current to only flow in one direction
What is the function of an LED?
Allows current to only flow in one direction, and produces light radiation
What happens to the resistance of a thermistor when the temperature changes?
The resistance of a thermistor decreases as the temperature increases.
What is the function of a thermistor?
Increases the resistance of a circuit depending on the temperature of the surroundings
What happens to the resistance of an LDR when the light intensity changes?
The resistance of an LDR decreases as light intensity increases.
What is the function of an LDR?
Increases the resistance of a circuit depending on the brightness of the surroundings
How are thermistors used?
in circuits as thermostats
How are LDRs used?
in circuits to switch on lights on when it gets dark
Give four examples of non-ohmic conductors
Diodes, filament bulbs, LDRs, thermistors
What is the unit for power?
Watts, W
What does the amount of energy an appliance transfers depend on?
how long the appliance is switched on for and the power of the appliance
What is the unit for energy transferred?
joules
What is the unit for work done?
joules
[ππΆπ΄π΅π²πΏ π§πΆπ²πΏ] In a transformer, which coil is the primary coil?
The coil with an alternating power supply connected to it
[ππΆπ΄π΅π²πΏ π§πΆπ²πΏ] In a transformer, which coil is the secondary coil?
The coil without an alternating power supply connected to it
What colour is the neutral wire?
blue
What is name of the blue wire in a plug?
neutral
What colour is the earth wire?
Green and yellow stripes
What is name of the green and yellow striped wire in a plug?
earth wire
What colour is the live wire?
brown
What is name of the brown wire in a plug?
live
What is the purpose of the neutral wire?
Completes the circuit
What is the purpose of the live wire?
Provides the alternating potential difference
What is the purpose of the earth wire?
Protects the circuit and stops the appliance casing from becoming live. It only carries current if there is a fault.
What is the pd of the neutral wire?
0 V
What is the pd of the live wire?
230 V
What is the pd of the earth wire?
0 V
What is the national grid?
a system of cables and transformers linking power stations to consumers
What is the potential difference of mains electricity?
230 V
What is the frequency of mains electricity?
50 hertz
What type of current is mains electricity
Alternating current (caused by an alternating potential difference)
What is direct current (d.c.)?
Current flows in one direction around the circuit, due to a direct potential difference. It is supplied by cells and batteries
What is alternating current (a.c.)?
Current changes (alternates) direction, due to a potential difference where the positive and negative ends alternate. It is supplied by mains electricity
Why does the national grid transmit electricity at very high potential differences?
Less energy is lost, which makes it more efficient
What happens at step-up transformers?
potential difference increased (current lowered)
What happens at step-down transformers?
potential difference lowered (current increased)
Why do we need step-down transformers?
Electricity has to be reduced to mains potential difference (230V) to be safe for use in homes