Litmux Studio

LabThe voltage divider · 15 min

Lab: a divider under load

A 10 k / 10 k divider on 12 V and a 10 kΩ load behind a switch. Measure the output, load it, then make the divider "stiffer" and see what it costs.

The circuit for: Lab: a divider under load
The circuit you start with

The steps

  1. Press RUN.RUN is on the toolbar (F5).
  2. Measure Vout across R2 with the multimeter on V⎓: 12 × 10 / 20 = 6.0 V.Red on R2's top end (the middle point), black on its bottom (0 V).
  3. Click S1 to connect the 10 kΩ load. Vout falls to 4.0 V: the load is in parallel with R2 (5 kΩ together).A click on a switch flips it while the circuit runs.
  4. Make the divider stiffer: change R1 and R2 to 1k each (same ratio). With the load still on, Vout is now 5.7 V - R1 ∥ R2 is only 500 Ω, twenty times less than the load.Double-click each resistor and type 1k. Rth = 500 Ω.
  5. The price: measure the current through R1 by Ohm's law - its voltage is 12 − 5.7 = 6.3 V, so 6.3 mA, against 0.8 mA before. Check it: put the meter across R1 (about 6.3 V).Move the leads to R1's two ends.

What it shows