Variable Resistor
Safety Warnings
Warning: Measurement Considerations
Purpose
Shows that resistance scales linearly with conductor length using a wire-wound rheostat and demo multimeter. Students observe direct evidence for \(R = \rho L/A\) by sliding a contact along the resistor and watching the resistance change in real time.
Figure 1:
The demo multimeter reads 4.3 Ω with the slider positioned near one end of the rheostat, giving a low resistance reading.
Figure 2:
With the slider moved further along the coil, the resistance increases to 59.6 Ω.
Figure 3:
The resistance reads 111.0 Ω with the slider near the middle of the coil.
Figure 4:
The resistance reads 167.0 Ω with the slider near the far end, approaching the maximum resistance of the rheostat.