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Solved exercise · level 3 of 5

Predict the cold resistance

Skills: Analyse

Statement

Wire F1 (aluminium, α = 0.004 /°C) has just been running: it is at 100 °C and the ohmmeter shows its hot resistance.

What will its resistance be once cooled to 20 °C? Answer, then watch.

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

3 hints from Bastaya available in the lab
Solution

R₂₀ = Rθ / (1 + α Δθ) = 18.48 / (1 + 0.004 × (100 − 20)) = 14 Ω.

Course sheet of the chapter : Ohm's law & resistance

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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