Practice: Solved Examples

Example 1: Least Count

A thermometer has markings at $10^{\circ}\text{C}$ and $20^{\circ}\text{C}$. There are 5 divisions between these two marks. What is the smallest reading (Least Count) of this thermometer?

Solution:

1. Temperature Difference: $20^{\circ}\text{C} - 10^{\circ}\text{C} = 10^{\circ}\text{C}$.
2. Number of Divisions: $5$.
3. Value of 1 Division: $$\frac{10^{\circ}\text{C}}{5} = 2^{\circ}\text{C}$$

Answer: The smallest reading this thermometer can take is $2^{\circ}\text{C}$.

Example 2: Kelvin Conversion

The room temperature is $25^{\circ}\text{C}$. What is this temperature in the Kelvin scale?

Solution:

1. Formula: $K = C + 273.15$
2. Substitute value: $K = 25 + 273.15$
3. Calculate: $K = 298.15$

Answer: The room temperature is $298.15 \text{ K}$.

Example 3: Identifying Errors

Rahul tries to measure the temperature of boiling water using a Clinical Thermometer. Why is this dangerous?

Solution:

• Range Limit: A clinical thermometer usually has a maximum range of $42^{\circ}\text{C}$.
• Boiling Point: Water boils at $100^{\circ}\text{C}$.
• Consequence: The mercury or alcohol will expand beyond the capacity of the tube, causing the thermometer to break or explode.

Answer: Never use a clinical thermometer for boiling water; always use a Laboratory Thermometer which goes up to $110^{\circ}\text{C}$.