On the label,'PRI' stands for 'primary' and refers to the sideof the transformer connected to the power coming into thehouse
On the label,'PRI' stands for 'primary' and refers to the sideof the transformer connected to the power coming into thehouse from the utility. 'SEC' stands for secondary and refersto the side of the transformer attached to the furnace.Suppose your electric power in the house is at voltage 120volts (like most houses) so the white (WHT) wire on thetransformer is attached to one side of the incoming power lineand the black (BLK) wire is attached to the other side of theincoming power line. In that configuration, only some of thecoils on the primary side are in use. The blue (BLU) andyellow (YEL) wires are attached to the furnace. Here 'VA'actually means 'watts' (volts times amps) and gives themaximum power which should be drawn from this transformer. Thenotation VAC means 'volts, alternating current?.
a. When it is hooked up as indicated, what is the ratio of turns in the active part of the primary coil to the turns in the secondary coil?
b. When it is drawing maximum power, what is the current going into the controls of the furnace? If the transformer were not heating up when in use, what would be the current coming into the transformer from the primary side when it is producing maximum power?
c. However. the transformer is observed to get hot when it is used. If you had an ammeter, how would you figure out how much heating was occuring in the transformer (in watts)? Explain what measurement you would make(draw a little circuit showing how you would connect the ammeter) and how you would use the results of the measurement to get the answer.