Physics
PhET Simulations
Ohm’s Law
By this time you have developed an understanding of the basic properties of electric charge. You have
investigated these properties in a state of charge being at rest; hence the name “electrostatics.” With an
understanding of these fundamental properties you are now ready to begin considering charge in
motion…electricity.
Go to the main PhET website at http://phet.colorado.edu/index.php. Select “On Line” under the Run
our Simulations heading. From this menu list select Physics then Electricity, Magnets and Circuits. From
here you can look for the Ohm’s Law icon.
Objectives: After careful study of this simulation you should be able to:
1. Explain how current is affected by voltage.
2. Explain how current is affected by resistance.
3. Develop a relationship between current, voltage and resistance.
1. Slide the buttons for the Voltage and the Resistance up and down.
a. Watch what happens to the Current (I) in the giant expression V = IR. Make some
sketches, use your words….explain what you see thus what you are learning about what
affects the current in a circuit.
b. Watch the circuit picture as you vary the Voltage and the Resistance. How does the
circuit model communicate changes in Voltage? In Resistance? In Current? Make
sketches, use your words…again explain what this simulation is teaching you about
voltage, resistance and current.
c. Which quantity, Voltage or Resistance, seems to affect the Current in a circuit more?
2. Current and Voltage:
a. For the first experiment pick a value for the Resistance and leave constant.
b. Create a table of 6 different voltages and record the resulting current.
Voltage (V)
Current (mA)
c. Your data should give you a good idea of how voltage affects current. Relying on your
understanding of the relationships “directly proportional” and “inversely proportional”
how would conclude Current is related to Voltage?
3. Current and Resistance:
a. For the second experiment pick a value for the Voltage and leave constant.
b. Create a table of 6 different Resistances and record the resulting current.
Resistance (Ω)
Current (mA)
c. Again, your data should give you a good idea of how resistance affects current. Once
again relying on your understanding of the relationships “directly proportional” and
“inversely proportional” how would conclude Current is related to Resistance?
4. The equation that relates Current, Voltage and Resistance together in one statement is known
as Ohm’s Law; named after George Simon Ohm who first discovered the relationship. Recalling
what you have learned about how Current is related to Voltage and how Current is related to
Resistance combine these two thoughts into a single statement… Ohm’s Law.