Topic P2- Electricity Flashcards
(30 cards)
What is the potential difference (or voltage)?
The driving force that pushes the charge round. It’s unit is the volt
What does a fuse symbol look like?
A rectangle with a horizontal line going through it
What does a resistor symbol look like?
A rectangle
What does a variable resistor symbol look like?
A rectangle with a arrow going through it at an angle
What does voltmeter measure?
Potential difference in volts
Placed in parallel
What does a LDR symbol look like?
A rectangle with a circle round it and two arrows going towards it
What does an ammeter measure?
Current in amps
Placed in series
At a constant temperature what is directly proportional to the current flowing through an ohmic conductor?
The potential difference across it
What else increases as the resistance increases with temperature in a filament lamp?
The current
What are the 4 steps to investigate the factors affecting resistance of a circuit?
1) Attach a crocodile clip to the wire level with 0 cm on the ruler. Attach the second crocodile clip to the wire 10 cm away.
2) Close the switch, then record the current through the wire and the potential difference across it. Open the switch, then move the second crocodile clip another 10 cm away
3) Repeat this for a number of different lengths of the test wire. Calculate the resistance using R=V/I
4) Plot a graph and a line of best fit. It should be directly proportional
What are the 5 steps to find a component’s I-V characteristic?
1) Set up the circuit with an ammeter, voltmeter, variable resistor, components and battery.
2) Begin to vary the variable resistor. This alters the current flowing through the circuit and the potential difference across the component.
3) Take several pairs of readings from the ammeter and voltmeter, repeat each reading twice more to get an average.
4) Swap over the wires connected to the battery, so the direction of the current is reversed.
5) Plot a graph of current against voltage
What is an LDR dependent on?
The intensity of light e.g. in bright light the resistance falls
What is a thermistor dependent on?
Temperature e.g. in hot conditions, the resistance drops
What are sensing circuits used for?
To turn on or increase the power to components depending on the conditions that they are in
What happens if you remove or disconnect one component in a series circuit?
The circuit is broken and they all stop
In series what is the same and what is shared?
Potential difference- shared
Current- same
Resistance- shared
In parallel what stays the same and what is shared?
Potential difference- same
Current- shared
What does adding a resistor in parallel do?
It increases the total current that can flow around the circuit. An increase in current means a decrease in the total resistance of the circuit
What are the 5 steps to investigate resistance?
1) build a series circuit with an ammeter, battery and resistor. Make note of the potential difference of the battery
2) Measure the current through the circuit using the ammeter. Calculate resistance using R=V/I
3) Add another resistor and repeat step 1-2 until you’ve added all your resistors
4) next, add another resistor, in parallel and repeat this experiment
5) plot a graph of the number of resistors against the total resistance of the circuit for both the series and parallel circuit.
What is alternating and direct current?
Alternating- by alternating voltages in which the positive and negative ends keep alternating
Direct- a current that is always flowing in the same direction
What is the mains UK supply and the frequency?
230v
50Hz
What is the blue neutral wire?
When the appliance is operating normally, current flows through the live and neutral wires. It is around 0v
What is the brown live wire?
The live wire provides the alternating potential difference- 230v
What is the green and yellow earth wire?
It stops the appliance casing from becoming live. It doesn’t usually carry a current.
