Key relationship
κ=3(α₂−α₁)ΔT/(2h); ytip≈κL²/2.
Physics · Practical apparatus
Bimetal-strip thermal bending
Bonded layers want to expand by different amounts. Their mismatch bends the strip. Reversing temperature change or swapping expansion coefficients reverses the bend direction.
Open the interactive experiment →Bimetal-strip thermal bending
இணைக்கப்பட்ட இரு உலோகங்கள் வேறுபட்டு விரிவதால் தகடு வளைகிறது. வெப்ப மாற்றக் குறி மாறினால் வளைவு திசை மாறும்.
Key notes, relationships and model limits
Practical tip
Bonded layers want to expand by different amounts. Their mismatch bends the strip. Reversing temperature change or swapping expansion coefficients reverses the bend direction.
Common trap
Bending depends on the difference between expansion coefficients, rather than either coefficient alone.
Model limits
equal layer thickness and Young modulus, perfectly bonded strip, small-curvature deflection approximation. Large deflections require a nonlinear beam model.
What you will learn
Adjust bimetal-strip thermal bending apparatus, observe its reading and derive the indicated physical quantity.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
With Δα=8×10⁻⁶/K, ΔT=50 K, h=1 mm and L=0.1 m, κ=0.6/m and tip deflection≈3 mm.
Why this matters
The model connects bimetal-strip thermal bending with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
If both layers have the same expansion coefficient, bending is?
- Maximum because both expand.
- Zero in this ideal model.
- A bend determined only by strip length.
Read the explanation
Zero in this ideal model.
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.