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Solved exercise · level 4 of 5

Line voltage drop: admissible resistance

Skills: Calculate

Statement

An outlying garage is lit by lamps totalling 300 W and heated by a 1000 W radiator, all rated at 230 V. The installation must work at a minimum voltage of 205 V while the meter voltage is 230 V. What resistance should each of the two line conductors have, approximately?

P = 1300 W · U = 230 V · Uₘᵢₙ = 205 V

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

I ≈ P / U = 1300 / 230 = 5.65 A; admissible drop 230 − 205 V over the two wires: R = (230 − 205) / (2 × 5.65) ≈ 2.21 Ω per conductor.

Course sheet of the chapter : Resistor networks

This chapter is covered by the paths: 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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