How to Check This Lab

Circuit Breaker Box.jpg   

  1. The student should place the lead of their multimeter on Leg 1 to ground for the first measurement. They should get between 12 and 15 volts.
  2. The student should place the lead of their multimeter on Leg 2 to ground for the second measurement. They should get between 12 and 15 Volts.
  3. The student should place the lead of their multimeter on Leg 1 and Leg 2. They should get between 24 and 30 volts.
  4. If you switch the multimeter leads, the voltage doesn't change.
  5. Leg 1 and Leg 2 are additive. Leg 1 to ground is 12 volts and Leg 2 to ground is 12 volts, so Leg 1 to Leg 2 is the sum 24V. This is because the transformer is center tapped. This means that you have 120V coming into the primary side of the transformer, and then it is transformed to 24V on the secondary side of the transformer. So, Leg 1 is 24V and Leg 2 is 0V. Because it is center tapped, we take from the center and put that to ground/neutral. This means that, in reference to my ground, Leg 1 is 12V away. In reference to Leg 2, it is also 12V away. However, between Leg 1 and Leg 2, you have the full 24V.

 

Transformer Drawing.  

Creative Commons License

Unless specified otherwise, any and all work on this page is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.