Electricity Flashcards
Define:
Current
The flow of electrical charge
Equation:
Charge
Q = It
Equation:
Potential Difference
V = IR
Required Practical:
Resistance
1) Attach a crocodile clip to wire with 0cm on the ruler
2) Attach the second crocodile clip to the wire about 10cm away fro the first clip. Write down the length of the wire between the clips
3) Close the switch, then record the current through the wire and the p.d across it
4) Open the switch, then move the second crocodile clip another 10cm along the wire. Close the switch again and record the new length, current and p.d
5) Repeat this for a number of different lengths of the test wire
6) Use your measurements of current and p.d to calculate the resistance for each length of wire using R = V/I
7) Plot a graph of resistance against wire length and draw a line of best fit
8) Your graph should be a straight line through the origin meaning resistance is directly proportional to length
Required Practical:
I-V Characteristics
1) Set up a circuit containing a Variable Resistor, Ammeter, Voltmeter and the Component you’re testing
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 to see how the potential difference across the component varies as the current changes. Repeat each reading twice more to get an average p.d at each current
4) Swap over the wires connected to the battery, so the direction of the current is reversed
5) Swap over te wires connected to the battery, so the direction of the current is reversed
6) Plot a graph of current against p.d for the component
Describe:
LDR
Light Dependent Resistor
As light intensity increases, resistance decreases
Describe:
Thermistor
As temperature increases, resistance decreases
Describe:
Potential Difference in series
Total potential difference is shared between the components
Describe:
Current in series
The same current flows through all components
Describe:
Resistance in series
Total resistance is the sum of all resistances of the components
Describe:
Potential Difference in parallel
Potential Difference is the same across all components
Describe:
Current in parallel
Total current is shared between branches
Describe:
Resistance in parallel
Adding a resistor in parallel reduces the Total Resistance
Required Practical:
Resistance in series
1) First, you’ll need to find at least four identical resistors
2) Then build a circuit using one of the resistors. Make a note of the potential difference of the battery
3) Measure the current through the circuit using R = V/I
4) Add another resistor, in series with the first
5) Again, measure the current through the circuit and use this and the potential difference of the battery to calculate the overall resistance of the circuit
6) Repeat steps 4 and 5 until you’ve added all of your resistors
7) Plot a graph of the number of resistors against the totall resistance of the circuit
Required Practical:
Resistance in parallel
1) First you’ll need to find at least four identical resistors
2) Then build a circuit using one of the resistors. Make a note of the potential difference of the battery
3) Measure the total current through the circuit and calculate the resistance of the circuit using R = V/I
4) Next, add another resistor, in parallel with the first
5) Measure the total current through the circuit and use this and the potential difference of the battery to calculate the overall resistance of the circuit
6) Repeat steps 4 and 5 until you’ve added all of your resistors
7) Plot a graph of the number of resistors in the circuit against the total resistance
Describe:
Mains Supply
Alternating Current
230V
50Hz
Describe:
Battery Supply
Direct Current
Describe:
Plug Sockets
Brown Live wire - 230V
Blue Neutral wire - 0V
Green and Yellow Earth wire - 0V
Equation:
Energy Transferred
E = Pt
E = QV
Equation:
Power
P = VI
Describe:
The National Grid
Giant system of cables and transformers
Connects power stations to consumers
Uses high potential difference and low current
Describe:
Step-up Transformer
More coils on primary coil than secondary coil
Increases potential difference
Decreases current
Describe:
Step-down Transformer
More coils on secondary coil than primary coil
Decreases potential difference
Increases current
Equation:
Transformers
P.D primary × Current primary = P.D Secondary x Current secondary
