Objective
The objective of this experiment is to observe the behavior of a varistor when subjected to overvoltage conditions and to analyze its protective characteristics.
Materials
- Varistor (e.g., MOV)
- Power supply (adjustable)
- Multimeter (for measuring voltage and current)
- Oscilloscope (optional, for waveform analysis)
- Resistors (for current limiting)
- Breadboard and jumper wires
- Safety goggles
Procedure
- Set up the circuit on a breadboard, connecting the varistor in parallel with the load.
- Connect the adjustable power supply to the circuit.
- Start with a low voltage and gradually increase the supply voltage while monitoring the multimeter readings.
- Record the voltage and current readings at different supply voltages, especially as it approaches the varistor's rated voltage.
- If available, use an oscilloscope to observe the waveform across the varistor.
- Continue increasing the voltage until the varistor activates or fails.
- Ensure safety measures are in place and discontinue the experiment if the varistor shows signs of overheating or damage.
Results
Record your observations and measurements in the table below:
| Supply Voltage (V) | Voltage Across Varistor (V) | Current Through Varistor (A) |
|---|---|---|
| 5 | 5 | 0.01 |
| 10 | 10 | 0.02 |
| 20 | 0 (varistor activated) | 0 |
Conclusion
The experiment demonstrated that the varistor effectively protects the circuit by clamping the voltage to a safe level when subjected to overvoltage conditions. This characteristic makes varistors valuable components in surge protection applications.