Physics

$A_1=\sqrt[]{{\left(5\right)}^2+{\left(5\sqrt[]{3}\right)}^2}=10$

$A_2=5$

Then, $\frac{A_1}{A_2}=\frac{10}{5}=\frac{2}{1}$

Yes, a material's resistivity will increase with the presence of impurities. This is because these impurities will occupy more surface area and disrupt the flow of electrons which will impact their free movement. As a result, the current cannot pass freely through the material and it will affect the resistivity.

Resistance is referred to the ability of an object to oppose the flow of electric current through itself. On the other hand, resistivity is the property of that particular material of resisting the passage of electric current over a particular unit area. Resistance has SI unit ohm whereas resistivity has ohm-metre.

In a cyclic process,   $\Delta U=0.$

In a cyclic process work done is equal to the area under the cycle and is positive if the cycle is clockwise and negative if anticlockwise 

$\Delta W=$ Area of rectangle $ABCD=-P\left(2V\right)$

$=-2PV$

According to first law of thermodynamics

$\Delta Q=\Delta U+\Delta W$ or $\Delta Q=\Delta W$ $\left(As\Delta U=0\right)$

i.e., heat supplied to the system is equal to the work done

So heat absorbed, $\Delta Q=\Delta W=-2PV$

Heat rejected by the gas $=2PV$

The primary reason for this is that silver is a quite expensive material to be used on such a large scale. Also, it doesn't have a much longer lifespan and tarnishes easily. So copper is used for electrical wiring because it offers low resistance to electric current is comparatively much more safer option to be commercially used.

Rate of heat radiated at (227 + 273) K

$=7cals/\left(c{m}^{2}s\right)$

Let rate of heat radiated at (727+ 273)  K = xcals/ (cm²s)

By Stefan's law 

$R=n^{1/3}r$

$E=T.\Delta A=ms\Delta TJ$

Energy stored in unit volume of wire

Water level in both section A and B will be goes up due being of centrifugal force water will goes away and it acquire the force from upside so the water will does up so water level in both the section A and B goes up.