Question 1

In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? 1. Area of the hole in the lid 2. Temperature of the flame 3. Weight of the lid

Accepted Answer

The temperature at which food is cooked in a pressure cooker depends mainly on the area of the hole in the lid, the temperature of the flame, and the weight of the lid. These factors collectively affect the pressure inside the cooker, which in turn influences the boiling point of water and the cooking temperature.

Question 2

The tendency of a liquid drop to contract and occupy minimum area is due to:

Accepted Answer

When a liquid drop is released from external forces, it naturally contracts and takes on a spherical shape. This behavior is caused by surface tension, a property of liquids that drives them to minimize their surface area.

Question 3

Assertion (A): A piece of copper and a piece of glass are heated to the same temperature. When touched, thereafter, the copper piece appears hotter than the glass piece. Reason (R): The density of copper is more than that of glass.

Accepted Answer

Both Assertion and Reason are correct. When both a piece of copper and a piece of glass are heated to the same temperature, the copper piece feels hotter to touch than the glass piece. This is because copper, being a metal, is a better conductor of heat compared to glass, which is a poor conductor. The reason for the difference in perceived temperature is due to the varying thermal conductivity of the materials.

Question 4

A hollow sphere of radius R, a hollow cube of side R and a thin circular plate of radius R, made up of the same material, are all heated to 20°C above room temperature. When left to cool in the room, which of them will reach the room temperature first?

Accepted Answer

In this scenario, the hollow sphere, hollow cube, and thin circular plate, all made of the same material and heated to 20°C above room temperature, are left to cool in the room. The sphere will reach room temperature first due to its maximum surface area, as heat loss is directly related to surface area.

Question 5

Consider the following natural phenomena: 1) Terrestrial heating 2) Reflection of light 3) Refraction of light 4) Diffraction of light. Due to which of these phenomena is a mirage formed?

Accepted Answer

In the natural world, various phenomena like terrestrial heating, reflection of light, refraction of light, and diffraction of light occur. A mirage is formed due to the combination of terrestrial heating and refraction of light. When the ground heats up, it causes the air above it to become warmer and less dense, leading to the refraction of light rays and the creation of a mirage.

Physics - Heat & Optics — UPSC Previous Year Questions

In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? 1. Area of the hole in the lid 2. Temperature of the flame 3. Weight of the lid

Year-wise Distribution

Sample Questions

Physics - Heat & Optics — UPSC Previous Year Questions

In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? 1. Area of the hole in the lid 2. Temperature of the flame 3. Weight of the lid

Year-wise Distribution

Sample Questions