Electricity
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Voltage
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Page 1
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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 Law
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 (R).
- 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 A. 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 the circuit.
- 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.