When a cylinder is heated,its length increases by $2\%$. What is the percentage increase in its surface area (in $\%$)?

$A$ circular disc with a hole is shown in the figure. On heating,if the outer diameter $d_1$ increases by $0.3\%$,then the inner diameter $d_2$ will

What must be the lengths of steel and copper rods at $0^o C$ for the difference in their lengths to be $10\,cm$ at any common temperature? $(\alpha_{steel}=1.2 \times 10^{-5} \;^o C^{-1})$ and $(\alpha_{copper} = 1.8 \times 10^{-5} \;^o C^{-1})$

$A$ steel tape gives correct measurement at $20^{\circ} C$. $A$ piece of wood is being measured with the steel tape at $0^{\circ} C$. The reading is $25 \ cm$ on the tape. The real length of the given piece of wood must be:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: When a rod lying freely is heated,no thermal stress is developed in it.
Reason $R$: On heating,the length of the rod increases.
In the light of the above statements,choose the correct answer from the options given below:

$A$ bimetallic strip consists of metals $A$ and $B$. It is mounted rigidly as shown. The metal $A$ has a higher coefficient of linear expansion compared to that of metal $B$. When the bimetallic strip is placed in a cold bath,it will: