Question

Two copper rods of same length, but of different diameters of cross section are given same amount of heat. Assuming no heat losses.

• A. Thick rod expands more
• B. Thin rod expands more
• C. Both rods expand equally
• D. For large quantities of heat thick rod expands more and thin rod expands more for small quantities of heat

Answer 1

The correct option is B Thin rod expands more

Heat given $Q=mS\Delta T$

The mass of thin rod is less than thick rod, so the rise in the temperature will be higher for thin rod.

$\Delta L=L\alpha \Delta T$.

So the rise will be more for higher $\Delta T$. Thin rod will expand more.