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Solved exercise · level 3 of 5

Measure the back-EMF of a motor

Skills: Measure, Calculate

Statement

Motor M1 has an armature resistance r′ = 0.5 Ω; V1 and A1 measure its voltage and current. Compute its back-EMF E′.

Parametric exercise: the values change with every draw; these are one example.

2 hints from Bastaya available in the lab
Solution

E′ = U′ − r′ · I = 12 V − 0.5 × 7.2 A = 8.4 V.

Course sheet of the chapter : Real generators & loads

This chapter is covered by the paths: General electricity, Measurement prep, ISL-oriented exercises

Other exercises of the chapter

Simulated time00:00:00
Q = I·t-
W = P·t-

Circuit diagram CEI 60617

How does it work?

Each big hole is a circuit node: you push one leg of a component into it. The 4 small holes around it are connected to it: chips and leads plug in there.

  1. Place a component Drag it from the palette: it snaps onto the grid. R rotates it.
  2. Bridge neighbouring holes Pick the jumper chip (or C) and drag on the board: bridged holes become a single node.
  3. Draw a lead For long links and the power supply: from one big hole to another, or to a terminal.
  4. Close the loop The circuit is solved live (Ohm, Kirchhoff) and the diagram follows.

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