PIRA 5F10.10 Ohm's Law: Ohm's Law / Series Resistors

Photo of the Demonstration at the University of Texas at Austin.

• This current edition of an Ohm's Law demonstration requires the use of an overhead projector.


• One can either vary the number of volts from 1 to 4 volts to show a linear rise in current - or - add up two more 10 ohm resistors in series to original 10 ohm circuit.


• The core of the demo is a simple circuit with three resistors wired in series to a 500 mA projection-ammeter


• The circuit board also houses a built-in DC volt meter, which is used to measure the input voltage from the power supply.


• The variable voltage DC power supply - which is an old CENCO unit - will usually be set to 3 volts at the start of the demonstration.


• Note: - projection voltmeter and ammeter used to measure voltage and current aren't the best - but most students will be able to at least view rise or fall of the ammeter needle.

• Demo Staff: Be sure to set the power supply output so that the volt meter displays 3 volts - before leaving the classroom.