Labo Élec

electrical lab simulator
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Exercise from the chapter "Real generators & loads"

Generalised Ohm's law: missing EMF

Level 4 of 5 · Skills: Calculate

Statement

Two generators (E₁ unknown and E₂ = 20 V) feed in series three loads with back-EMFs 10 V, 10 V and 9 V. The sum of all circuit resistances (internal and external) is ΣR = 5 Ω and the current is I = 2 A. What is E₁?

E₂ = 20 V · ΣE′ = 29 V · ΣR = 5 Ω · I = 2 A

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

Guided problem in 4 steps: unknown, formula, units, data, result.

1 hint from Bastaya available in the lab
Solution

ΣE = ΣE′ + ΣR · I → E₁ + E₂ = 29 + 5 × 2; E₁ = 29 + 5 × 2 − 20 = 19 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-

Workbench

Circuit diagram CEI 60617

How does it work?

The perfboard: each big hole is a circuit node. You push a single leg of a component (resistor, lamp...) into it. The 4 small holes around it are connected to it: that is where chips and leads plug in.

  1. Drag a component onto the board: it snaps onto the grid. R rotates it.
  2. To join neighbouring big holes, click Jumper chip in the palette (or C) then drag on the board: a line of chips is laid at once. Bridged holes become a single node.
  3. For long links and for the power supply (placed next to the board), drag a lead from one big hole to another (or to a terminal).
  4. As soon as a loop is closed, the circuit is solved in real time (Ohm + Kirchhoff) and the diagram follows.
  5. Zoom with the wheel (or + / −, two-finger pinch); drag the background to pan, 0 fits the board. The + buttons around the board add a row or a column.

Del delete · R rotate · C chip brush · Esc cancel · wheel zoom · drag the background to pan

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