Video: Watch this demo
Description: This demonstration shows the basic function of a transformer. When the primary coil is connected to an AC power supply an altered voltage can be read read off of the secondary coil. Can show a step up or step down transformer (depending on which coil is primary).
Equipment:
- 1000 turn coil
- 500 turn coil
- Variac power supply
- Variac to banana plug cable
- 2 AC voltmeters
- 4 long banana cables
- Induction C rod and L rod
Setup Procedure:
- Place the two coils on the Induction C rod, then clamp the L rod over the central post and tighten the screw
- Connect a voltmeter to each coil and set the meters to the correct range (Ex: 30VAC, Left, AC)
- Connect the Variac to the primary coil (Last step so that the professor can easily change between coils)
Demonstration Procedure:
- Check that each meter is reading the voltage of a coil
- Display the meters on the overhead projector.
- Turn on the Variac and slowly raise the voltage (don’t go above 30V!) Do not touch the coils when they are powered
- Note the voltage response of the coils
– If the primary has fewer turns than the secondary, you should note the secondary coil has a larger voltage (Step Up transformer)
– If the primary has more turns than the secondary, you should note the secondary coil has a lower voltage (Step Down transformer) - Turn off the Variac, and switch the Variac leads to the other coil to try the other configuration
- When finished, turn off the Variac
Note: Calculating the theoretical step up or step down voltage on the secondary can be preformed using the # of turns of each coil, however coils are not 100% efficient in real life
