Part A: Investigating the relationship between potential difference, current and resistance for a resistor and a filament lamp. Flashcards
Outline the basic steps of the practical
- Set up a circuit with a voltmeter attached in parallel to a resistor and an ammeter attached in series to the resistor
- Start on a low voltage and slowly increase the voltage, recording the potential difference and current values each time
- Repeat, swapping the resistor for a filament lamp
Plot a graph of current against potential difference for both
components
Draw a circuit diagram for this set up
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What two types of meters are needed in the circuit, and how should they be connected?
- Voltmeter: Connected in parallel to the component
2. Ammeter: Connected in series with the component
What component is required to alter potential difference if you’re not using a variable power pack?
A rheostat, or variable resistor.
What is an ‘Ohmic Conductor’? State the condition required
●A conductor for which current and potential difference are directly proportional
● Resistance remains constant as current changes
● Temperature must be constant
What must be kept constant to get reliable results? How can you achieve this?
Temperature should remain constant so that the resistance of the components isn’t affected. You should disconnect the supply when not taking readings to avoid
unnecessary heating
How does temperature affect resistance?
Temperature causes an increase in
resistance.
How do you determine the resistance of
a component from an I-V graph?
The resistance at a given point is the inverse of the gradient of the line drawn from that point to the origin.
What would you expect the I-V graph of a fixed resistor to look like?
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What would you expect the I-V graph of a filament lamp to look like?
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What happens to the resistance of a filament lamp as the temperature increases? Why?
● Resistance increases
● Ions in metal have more energy, so vibrate
more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow
