Welcome to the Voltage Circuit Simulator
This excercise will help you determine the relationship between voltage
(V), amperage (I) and resistance (R). This relationship is called Ohm's
This experiment consists of modifying a circuit. The circuit is made
up of four parts:
- a battery : A battery has a positive
and negative terminal that creates a potential difference. This is frequently,
but erroneously, taken as being equivalent to potential energy. They are
not identical. Potential difference is proportional to potential energy
and the two can be related via the work done per unit charge. This measure
of energy per unit charge is measured is called voltage (V)
and the unit of measurement is called volts.
- a wire, which has resistance (R). Resistance inhibits
the amount of current running along the circuit. The greater the resistance,
the lower the current. Resistance is a bit like inertia in mechanics. For
a given force, the greater the mass (inertia) the lower the acceleration.
Here, for a given voltage, material with high resistivity will inhibit
the flow of electrons (\eg current) through it.
- a lightbulb which has an amperage
(I). Amps are the unit of current and current is the amount of electrons
that flow down the wire per unit time. This current is converted to power
by the resistive element inside the light bulb. The length of time that
you leave the light bulb on determines the total amount of energy which
has been used.
- a switch, which turns the system on and off.
The problem consists of two parts:
- Find the formula which describes Ohm's Law; that is, find the mathematical
relationship between voltage (V), amperage (I), and resistance
- Determine the amperage of the lightbulb.
The first part will be discovered through a trial-and-error experiment.
You are given a circuit on which you may vary the voltage by choosing from
a variety of batteries and the resistance by adding resistors
to the circuit. You will then turn on the switch, allowing current to flow
through the circuit. If the resistance is too low, the lightbulb will receive
too much current, and will explode. If the resistance is too great, the
lightbulb will not receive e nough current, and will not light. If the
resistance is just right, the lightbulb will light up. (Note: real light
bulbs are not perfect ohmic resistors as is the case here and will light
partially with any amount of current).
If the lightbulb explodes or fails to light, turn off the switch (which
automatically replaces the lightbulb) and try again.
First, concentrate on changing the resistance to get the lightbulb to
turn on. Once you get a working circuit write down your values, change
the value of the battery, and try again. You should begin to see the relationship
between V, I, an d R. You should then be able to derive
what the Amperage of the lightbulb is.
Each battery and resistor has a value printed on it which reflects the
objects voltage and resistance, respectively.
- To add batteries to the circuit, use the mouse to drag a battery from
the toolbox (the box containing the various resistors and batteries) and
drop it onto the larger battery on the circuit.
- To add resistors to the circuit, drag a resistor from the toolbox onto
the empty box located on the circuit. Multiple resistors may be added to
- To remove resistors, simply drag the resistor you wish to remove from
the circuit and drop it anywhere outside of the resistor box.
- To turn the circuit on and off, click once on the switch.
Now that you know Ohm's law, you can apply
it to a circuit where all values are known.
In this next circuit, the lightbulb has a different amperage than in
the previous experiment. Furthermore, we will tell you what the amperage
of the lightbulb is. Given this information, you should be able to complete
the circuit correctly with one try.
Try this circuit
Applet coding by Sean Russell
Graphic images by Amy Hulse
Content by Greg Bothun