Page 149 - Knowledge Organiser Yr9 24-25

Knowledge Base/Builder: Science P2: Electricity Year 9
3. Current, potential difference and resistance
3.1
What symbol is used instead of writing the words "potential difference"?
V
3.2
What is the unit of potential difference?
Volts or V
3.3
What symbol is used instead of writing the word "resistance"?
R
3.4
What is the unit of resistance?
Ohms or Ω
3.5
State the equation that links current, potential difference and resistance.
Potential difference = current x time
3.6
Give the symbol equation that links current, potential difference and resistance.
V=IR
Worked example question:
A 4.0Ω resistor in a circuit has a potential difference of 6.0V across it. What is the current through the resistor?
3.7
State the potential difference rule for components connected in series.
Potential difference of the power supply is shared between the components.
3.8
State the potential difference rule for components connected in parallel.
The potential difference is
the same across each branch of the circuit.
4. Knowledge Builder – Resistance required practicals: Resistance Part 1
Describe a method to carry out an experiment to investigate how resistance is affected by the length of the wire.
1. Setupthecircuitasshowninfigure1below,usingcrocodileclipstoattachtothewire.
2. Place a meter ruler behind the length of wire.
3. Attach crocodile clips to the wire at 0m and at 0.1m so that 0.1m of wire is connected in the circuit.
4. Close the switch and record the current on the ammeter and the potential difference on the voltmeter.
5. Switch and wait 30 seconds.
6. Repeat steps 4 and 5, 2 more times to collect repeat measurements.
7. Keep repeating the process, increasing the distance between the crocodile clips by 0.1m each time until you have reached 1m.
8. Calculate the mean current and potential difference for each length and use the means to calculate resistance using the equation.
Figure 1:
Circuit diagram for required practical "resistance part 1."
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