# iLab at Iona Prep

## Resistor Puzzle:

Measure the resistance of three unknown resistors.

You have a circuit with three resistors R1, R2, R3. They are wired in series and connected to a 5.0 volt power supply. Resistors R1 and R2 each have a relay connected aross them. Activating the relay will short circuit the resistor, effectively removing it from the circuit. There is also an ammeter which measures the current through the circuit.

You may activate no relay, or the relay across R1, or the relay across R2 and measure the current through the circuit. By repeating this experiment you should be able to calculate the resistance of each of the three resistors.

Remember that no power supplies or ammeters or resistors are perfect.  Therefore you should not rely on any single measurement.  Make multiple measurements (perhaps 10) then compute the average and use the average in your calculations.  Keep 3 significant figures in your calculations and then express your final answers to two significant figures. (The resistance of a resistor is normally expressed to two significant figures.)

This is the experimental setup: The power supply is at the top. The white device is called a breadboard. Along the top of the breadboard are the three resistors. The black rectangles are the relays. The wires go off to the computer.