Wednesday, 27 November 2013

Tansformer power measurements

This experiment will allow you to perform a basic investigation of the power transfer & efficiency of a simple transformer.


Power supply (12V a.c )
12V bulb
Variable resistor
Two a.c Voltmeters
Tw a.c Ammeters (multimeters could be used)
Connecting leads with croc clips
Wire for winding (laminated or insulated)
Iron rod 15 - 20 cm long


From the power supply attach the variable resistor and one ammeter in series. Create a primary coil of fifty turns around one end of the iron rod using the winding wire and use croc clips to connect this pimary coil in series with the ammeter and variable resistor back to the power supply. Connect one voltmeter in parallel across the primary coil.

Create a secondary coil at the other end of the iron rod, again using fifty turns. Using crocodile clips connect the bulb and the second ammeter in series with the secondary coil and connect the voltmeter in parallel to teh secondary coil.

With the variable resistor turned completely one way not the readings on all of the meters.

Turn the variable resistor and take readings in five to ten different positions until the variable resistor reaches the other limit of rotation.

Repeat twice more, using the variable resistor to give your the same values for current and voltage on the primary coil each time.


Find the mean readings for each step and then use the equation P = I V to find the power on the primary and the power on the secondary.

Plot a graph of the input and output power and describe any relationships you notice. Why is there a discrepancy in the power between each side?