4.Main Content
experiments
Oscilloscope and alternating voltage from transformer
Demonstration
A way of showing quantitatively the relationship between the e.m.f. and turns ratios of transformer coils.
Apparatus and materials
- Oscilloscope
- Demountable (demonstration) transformer with coils of 12 000 and 300 turns
- Leads, 4 mm, 2
Technical notes
The mains lead to the 12,000 turn coil should be permanently connected; 4 mm leads connected to a 13 A mains plug are a serious hazard.
If the coil fitted with a mains connector has only 12,00 turns, reduce the secondary to 30 turns. Do not improvise mains connections with 4 mm leads.
Safety
The 1,200 coil must be designed for use on the mains, i.e. the mains lead must be permanently attached or connected via an IEC connector.
Read our standard health & safety guidance
Procedure
Photo courtesy of Mike Vetterlein
a Set up the demountable transformer with the 12,000-turn coil on one side of the U-core and the 300-turn coil on the other.
b Plug the 12,000-turn coil into the (230 V) mains. There will then be about 6 volts across the secondary coil when the core is completed.
c Connect the low-voltage output from the secondary of the demountable transformer to the Y-plates of the oscilloscope by direct connection to the input terminals.
Teaching notes
1 The frequency of the AC mains can be calculated from the time-base reading.
2 The turns ratio and the voltage ratios can be compared.
This experiment was safety-checked in April 2006