Bomb Calorimeter – SSC JE 2018 Question

The Bomb Calorimeter is a classic laboratory instrument used in thermal engineering to measure the calorific value of fuels.
Here’s a question from SSC JE 23.01.2018 (Morning Shift).

Question:

The bomb calorimeter is an apparatus to measure the:

(a) Calorific value of a gaseous fuel / गैसीय ईंधन का ऊष्मीय मान
(b) Calorific value of solid and gaseous fuels / ठोस और गैसीय ईंधन के ऊष्मीय मान
(c) Calorimetric composition of any solid bomb material / किसी भी ठोस बम सामग्री की कैलोरीमेट्रिक संरचना
(d) Calorific value of a solid or liquid fuel / ठोस या तरल ईंधन के ऊष्मीय मान

Video Solution

In my video explanation, I’ve shown how a bomb calorimeter works with a schematic diagram and how to calculate the calorific value using the temperature rise in water.

Watch Full Video Solution

Correct Answer:

(d) Calorific value of a solid or liquid fuel / ठोस या तरल ईंधन के ऊष्मीय मान

Explanation:

• The Bomb Calorimeter measures the heat of combustion of a known quantity of fuel.

• It is particularly used for solid (e.g., coal, biomass) and liquid fuels (e.g., fuel oil).

• The fuel is burned in a strong steel vessel (the “bomb”) surrounded by water.

• The temperature rise of water is measured to determine the calorific value.

Working Principle:

1. A weighed fuel sample is placed inside the bomb.

2. The bomb is filled with oxygen at high pressure.

3. The bomb is submerged in a known quantity of water.

4. Fuel is ignited electrically, releasing heat.

5. Temperature rise of the water is recorded.

6. Calorific value is calculated using:

   $$CV = \frac{(m_w C_w + m_c C_c) \Delta T}{m_f}$$

   Where:

   • $m_w$ = Mass of water

   • $C_w$ = Specific heat of water

   • $m_c$ & $C_c$ = Mass & specific heat of container

   • $\Delta T$ = Temperature rise

   • $m_f$ = Mass of fuel burned

Key Points for Exams:

• Solid/Liquid fuels → Bomb Calorimeter

• Gaseous fuels → Junker’s Gas Calorimeter

• The bomb calorimeter works on the principle of constant volume combustion.

Tip: If you see “Bomb Calorimeter” in the exam, always remember: solid/liquid fuels and constant volume combustion.