Solved Problems on Thermal Physics | 10th Grade Science Chapter 3

Solved Problems: Thermal Physics

Example 1

A container whose capacity is 70 ml is filled with a liquid up to 50 ml. Then, the liquid in the container is heated. Initially, the level of the liquid falls from 50 ml to 48.5 ml. Then we heat more, the level of the liquid rises to 51.2 ml. Find the apparent and real expansion.

Data:

• Level of the liquid L₁ = 50 ml
• Level of the liquid L₂ = 48.5 ml
• Level of the liquid L₃ = 51.2 ml

Solution:

Apparent expansion = L₃ − L₁

= 51.2 ml – 50 ml = 1.2 ml

Real expansion = L₃ − L₂

= 51.2 ml – 48.5 ml = 2.7 ml

So, Real expansion > apparent expansion.

Example 2

Keeping the temperature as constant, a gas is compressed four times of its initial pressure. The volume of gas in the container changing from 20cc (V₁ cc) to V₂ cc. Find the final volume V₂.

Data:

• Initial pressure (P₁) = P
• Final Pressure (P₂) = 4P
• Initial volume (V₁) = 20 cc = 20 cm³
• Final volume (V₂) = ?

Solution:

Using Boyle's Law, PV = constant. Therefore:

\( P_1 V_1 = P_2 V_2 \)

To find \(V_2\), we can rearrange the formula:

\( V_2 = \frac{P_1 V_1}{P_2} \)

Substituting the given values:

\( V_2 = \frac{P \times 20}{4P} \)

\( V_2 = \frac{20}{4} = 5 \text{ cc} \)

The final volume V₂ is 5 cc.