alleryWhat is the SI unit of thermal conductivity K?
- W m–2
- W m–1 K–1
- J K–1
- J kg–1 K–1
Show answer and solution
Correct answer: B. W m–1 K–1
From H = K A ΔT/L, K has unit watt per metre per kelvin.
CBSE Class 11 (Science) Thermal Properties of Matter & Thermodynamics — practice questions — page 9
Explore 267 free Thermal Properties of Matter & Thermodynamics questions in CBSE Class 11 (Science) Physics. Open each question or exercise to read its content, reference answers and available explanation.
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What is the SI unit of thermal conductivity K?Read the answer and worked solution →A bar's length is doubled, with the same end temperatures and area. What happens to heat current?Read the answer and worked solution →Two identical rods are placed side by side to act as one wider rod, ends at same temperatures. Heat current becomes what?Read the answer and worked solution →A rod has K = 400 W m–1 K–1, A = 1.0 × 10^-4 m², L = 0.5 m and ends 100 K apart. What is the heat current?Read the answer and worked solution →A material has a larger thermal conductivity. How does it conduct heat?Read the answer and worked solution →Natural convection is responsible for which of these?Read the answer and worked solution →Which of these is an example of forced convection?Read the answer and worked solution →Which steady surface wind blows from the north-east towards the equator?Read the answer and worked solution →Which mode of heat transfer needs no material medium?Read the answer and worked solution →Why do people prefer light-coloured clothes in summer?Read the answer and worked solution →Why are the bottoms of cooking utensils blackened?Read the answer and worked solution →What is the purpose of the silvered walls of a Dewar flask?Read the answer and worked solution →What kind of spectrum does thermal radiation at any temperature have?Read the answer and worked solution →A star's peak emission is at 2.9 µm. With Wien's constant 2.9 × 10–3 m K, what is its surface temperature?Read the answer and worked solution →The absolute temperature of a blackbody doubles. By what factor does radiated power change?Read the answer and worked solution →What is the emissivity e of a perfect radiator?Read the answer and worked solution →As iron is heated in a flame, what colour sequence does it show?Read the answer and worked solution →Newton's law of cooling holds good only when the temperature difference is what?Read the answer and worked solution →Blackbody radiation curves depend on which property of the body?Read the answer and worked solution →Match each thermal expansion coefficient with its relationship:Read the answer and worked solution →Match each heat radiation law with its mathematical statement:Read the answer and worked solution →Match each thermal conductivity parameter with its formula:Read the answer and worked solution →Match each thermodynamic state property of water with its anomaly:Read the answer and worked solution →Match each thermodynamic law with its foundational statement:Read the answer and worked solution →Match each thermodynamic state function with its definition:Read the answer and worked solution →Match each condition of spontaneity with the sign of Gibbs Free Energy change (ΔG):Read the answer and worked solution →Match each thermodynamic process with its constraint:Read the answer and worked solution →
Worked practice questions
A bar's length is doubled, with the same end temperatures and area. What happens to heat current?
- It is unchanged
- It is four times
- It is halved
- It is doubled
Show answer and solution
Correct answer: C. It is halved
H is inversely proportional to length, so doubling L halves H.
Two identical rods are placed side by side to act as one wider rod, ends at same temperatures. Heat current becomes what?
- Unchanged
- Doubled
- Quartered
- Halved
Show answer and solution
Correct answer: B. Doubled
Cross-sectional area doubles while length and temperature difference stay equal, so H doubles.
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