I-V Characteristics - AQA Practical

AQA GCSE Physics Electricity required practical: evaluating current-voltage characteristics and graphs of fixed resistors, filament lamps and diodes.‍ ‍Combined & Triple Science.

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Plan a valid method to investigate the current-voltage relationship of three components:

• fixed resistor 

• filament lamp

• diode
  

[6 marks]

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1. Prepare to test fixed resistor

• What basic components do we connect?

  • 6 V cell to power the circuit

  • Switch

  • the first component we’re testing: Fixed Resistor

• How do we measure current and voltage?

  • Ammeter in series

  • Voltmeter in parallel

• How do we change the voltage (potential difference) values?

  We add a variable resistor.

  We adjust the variable resistance to control the voltage shown on the Voltmeter to values near 0V, 1V, 2V etc.

2. Record Readings

• What readings do we take for the first resistor?

  • Voltage (potential difference) shown on voltmeter (we generate those values by adjusting the variable resistor)

  • Current in Amps shown on ammeter

  Adjust the variable resistor to obtain different potential differences from 0V to 6V (in 1V intervals) and, therefore, different current readings.

• How do we obtain negative values of voltage and current for our graph?

  • Turn off switch

  • Reverse connection of the battery,

  • Turn switch back on and take the same readings

3. Plot

• How do we evaluate the relationship between Current and Voltage for our tested component (fixed resistor)?

  • Plot an I-V graph

  • (current on the y axis, voltage on the x axis)

4. Change Component

to filament lamp, then diode

• How do we do the same for a filament lamp?

  • Turn the switch off, and replace the fixed resistor with a filament lamp

  • Turn the switch back on and repeat the entire process

• How do we do the same for a diode?

  • Turn the switch off, and replace the filament lamp with a diode

  • Turn the switch back on and repeat the entire process

Challenge:

• Why must we keep the fixed resistor's temperature constant during the experiment?

  Increasing the temperature increases the resistance of the fixed resistor. This would affect the current readings and prevent us from obtaining a straight-line I–V graph.

• Why does almost no current flow through a diode when the potential difference is negative?

  • A diode only allows current to flow easily in one direction. When the potential difference is reversed, the diode blocks the current, so almost no current flows.

  • Therefore, for negative potential differences, the current is approximately zero, so the graph stays close to the x-axis.

Continue Revising Paper 1

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