Labo Élec

electrical lab simulator
0 1 / 20

Exercise from the chapter "AC power"

Cos φ of a coil in parallel with a resistor

Level 5 of 5 · Skills: Calculate

Statement

A coil (R₁ = 10 Ω, L = 50 mH) is connected in parallel with a resistor R₂ = 38 Ω across a 220 V, 50 Hz supply. Compute the cos φ of the circuit (power method: P and Q of each branch).

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

2 hints from Bastaya available in the lab
Solution

Coil: Z = 18.6 Ω, P₁ = R₁·U²/Z², Q₁ = Lω·U²/Z²; resistor: P₂ = U²/R₂, Q₂ = 0; P = 2670 W, Q = 2190 var; cos φ = P / √(P² + Q²) = 0.773; I = S / U = 15.7 A.

Course sheet of the chapter : AC power

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-

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

Confirmer

Importer un montage

Export