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Solved exercise · level 3 of 5

Admissible switch-off time

Skills: Calculate

Statement

How long, at least, must the switch-off of a 3 H coil carrying 20 A last so that the self-induced EMF does not exceed 150 V?

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

2 hints from Bastaya available in the lab
Solution

Δt = L · ΔI / E = 3 × 20 / 150 = 0.4 s: the faster the cut, the larger the overvoltage.

Course sheet of the chapter : Induction & self-induction

This chapter is covered by the paths: General electricity, 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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