Question

Two chairs (A and B) are in an empty room overnight. Chair A is made of steel while chair B is made of wood. In the night and in the morning, the temperature of the room is 290 K. In the morning, a person chooses between Chair A and Chair B as the seat by feeling (touching) the chair and choosing one which feels warmer. 
Person chooses __ (BLANK-1) __ as it feels warmer because __ (BLANK-2)___ has __(BLANK-3)___ ___ (BLANK-4)____ than ___(BLANK-5)___ .

• A. BLANK-1: Chair A, Chair B, neither chair
• B. BLANK-2: metal, wood, air, human body
• C. BLANK-3: higher, lower, different, same
• D. BLANK-4: heat capacity, heat conductivity, electrical resistance

Hint:

Heat conductivity determines how easily heat flows from a material to the skin. Metals typically have higher thermal conductivity than wood.

Answer 1

The Correct Option is A

1. Thermal Equilibrium: Both chairs (A - steel, B - wood) have been in the room overnight at a constant temperature of 290 K. This means both chairs are actually at the same temperature (290 K).
2. Human Body Temperature: A person's body temperature (specifically, their hand) is typically around 310 K (37 °C).
3. Sensation of Temperature: When a person touches an object colder than their hand (like the chairs at 290 K), heat flows from their hand to the object. The sensation of "coldness" or "warmness" (in this case, relative warmness) depends on the rate at which heat is transferred away from the hand.
4. Thermal Conductivity: The rate of heat transfer is determined by the material's thermal conductivity (or heat conductivity).
   • Steel (Metal): Has a high thermal conductivity. It conducts heat away from the hand quickly, making it feel cold.
   • Wood: Has a low thermal conductivity. It conducts heat away from the hand slowly, making it feel relatively warmer than the steel (even though it's at the same actual temperature).
5. Choice (BLANK-1): The person chooses the chair that *feels* warmer. Since wood conducts heat away slower, Chair B (wood) feels warmer than Chair A (steel). Correct choice: Chair B
6. Reasoning (BLANKS 2-5): The reason Chair B feels warmer is related to the properties of its material (wood) compared to the other chair's material (metal). Specifically, wood feels warmer because its rate of heat transfer is lower due to its lower thermal conductivity compared to metal.
   • BLANK-2: The material being discussed that feels warmer is wood. Correct choice: wood
   • BLANK-3: The comparison of the property: wood's conductivity is lower. Correct choice: lower
   • BLANK-4: The relevant property determining the rate of heat flow is heat conductivity. Correct choice: heat conductivity
   • BLANK-5: The material wood is being compared to is metal (steel). Correct choice: metal

Assembled Sentence: Person chooses Chair B as it feels warmer because wood has lower heat conductivity than metal.

Answer 2

Both chairs — one made of steel (Chair A) and one made of wood (Chair B) — are in a room at the same temperature of $290\,\text{K}$ overnight.
In the morning, a person touches the chairs to feel which one is warmer. Even though both chairs are at the same temperature, they feel different to the touch due to the difference in thermal conductivity.
Metals (like steel) have a high thermal conductivity, meaning they can transfer heat quickly. When you touch Chair A (steel), it conducts heat away from your skin rapidly, making it feel colder.
Wood, on the other hand, is a poor conductor of heat. It does not transfer heat away from your body efficiently, so it feels warmer even though it's at the same temperature.
Therefore, the person chooses Chair B because it feels warmer. 

Filled Blanks:
Person chooses Chair B (BLANK-1) as it feels warmer because metal (BLANK-2) has higher (BLANK-3) heat conductivity (BLANK-4) than human body (BLANK-5).