Ohm's Law: Current, Voltage, and Resistance
1 · Predict
A 9 V battery drives current through a single resistor. If you use a bigger resistor, does more or less current flow?
- A bigger resistor means less current flows.
- A bigger resistor means more current flows.
- Current doesn't depend on resistance.
2 · Set Up
- Open the single-resistor preset and press Reset. The battery supplies a fixed 9 V.
- Enable the current readout on the resistor.
- Set the resistor's value for each trial and record the current.
3 · Collect Data
| Resistance R (Ω) | Power dissipated P (W) | Current I (A) |
|---|---|---|
| 50 | ||
| 100 | ||
| 200 |
Plot current I (y-axis) against 1/R (x-axis) for your three trials. Is the line straight through the origin?
4 · Analyze
- For one trial, compute I = E/R using E = 9 V. Compare to the table.
- Explain why doubling the resistance halves the current, using Ohm's law I = E/R at fixed voltage.
5 · Extend
- Your power column (P = E²/R) shrinks as resistance grows, even though voltage stays fixed. Explain why a bigger resistor draws less power from the same battery.
- What would happen to the current (and the battery) if R were set to nearly 0 Ω? Why do real circuits avoid this 'short circuit' condition?
The Physics Behind This Experiment
Ohm's Law
The current through a resistor is proportional to the voltage across it and inversely proportional to its resistance: I = V/R. Here V equals the full battery EMF, 9 V.
Electrical Power (from V and R)
Power dissipated by a resistor can be computed directly from voltage and resistance without needing current: P = V²/R.