Electricity and magnetism
Electric current
Observe DC current through a model of drifting electrons in a wire. Verify and the roles of cross-section and carrier density in .
⚠ Virtual simulation; when measuring real current, connect the ammeter in series and never across a voltage source — short-circuit hazard.
Equipment
- Virtual metal wire with moving free-electron dots
- Current slider (1–8)
- Sliders for relative cross-section and carrier density
- Time slider and a charge counter
Procedure
Track electron drift and conventional current
Run the simulation: blue dots (electrons) drift one way while the red arrow — conventional current — points opposite. Electrons show random thermal motion plus a small drift; conventional current runs from the positive to the negative terminal.
Count charge versus time
Set a current value and drag the time slider: accumulated charge grows proportionally, . Read the counter at two instants and check that stays constant for steady current.
Vary cross-section and carrier density
Hold I fixed and increase cross-section A: for the same current, the drift speed must fall per . Vary density n similarly. Predict first whether electrons drift faster or slower in a thinner wire, then observe.