Ohm's law with alternating current
Practical Activity for 14-16
An ohmic resistor is equally ohmic when used with alternating current.
Apparatus and Materials
- Power supply, AC, low voltage variable
- Rheostat (10 - 15 ohms)
- Ammeter, (0-1 A), AC
- Voltmeter, 0 to 15 V, AC
- Leads, 4 mm, 6
Health & Safety and Technical Notes
- Set up a simple series circuit using the AC terminals of the low-voltage supply in series with the ammeter and the rheostat, used here as a fixed resistor.
- Connect the voltmeter in parallel with the resistor. Adjust the voltage so that a current of about 1 A flows.
- Record a series of values of the current and potential difference as you gradually reduce the voltage applied.
- You can calculate the value of the resistance from the root mean square (rms) readings of current and voltage.
- The resistance will be the same value as in an experiment carried out with the same resistor using a DC supply.
This experiment was safety-tested in October 2006