Related InterviewSolutions

• A ball is dropped on a floor from a height of `2.0m`. After the collision it rises up to a height of `1.5m`. Assume that `40%` of the mechanical energy lost goes as thermal energy into the ball.Calculate the rise in the temperature of the ball in the collision.Heat capacity of the ball is `800J K^(-1)`
• A wall has two layers A and B, each made of different material. Both the layers have the same thickness. The thermal conductivity of the material of A is twice that of B . Under thermal equilibrium, the temperature difference across the wall is `36^@C.` The temperature difference across the layer A isA. `6^@C`B. `12^@C`C. `18^@C`D. `24^@C`
• A rod is heated at one end as shown in figure. In steady state temperature of different sections becomes constant but not same. Why so? .
• Show that the SI units of thermal conductivity are `W//m-K`.
• Three discs, A, B and C having radii 2m, 4m and6m respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are `300nm, 400nm` and `500 nm`, respectively. The power radiated by them are `Q_A, Q_B and Q_C` respectively (a) `Q_A` is maximum (b) `Q_B` is maximum (c) `Q_C` is maximum (d) `Q_A = Q_B = Q_C`
• A spherical black body with a radius of 12 cm radiates 450 W power at 500 K. If the radius were halved and the temperature doubled, the power radiated in watt would be (a)225 (b)450 (c) 900 (d)1800
• Assertion : A normal body can radiate energy more than a perfectly black body. Reason : A perfectly black body is always black in colour.A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. If Assertion is true, but the Reason is false.D. If Assertion is false but the Reason is true.
• The intensity of radiation emitted by the sun has its maximum value at a wavelength of 510 nm and that emitted by the North star has the maximum value at 350 nm. If these stars behave like black bodies, then the ratio of the surface temperatures of the sun and the north star isA. 1.46B. 0.69C. 1.21D. 0.83
• Assertion : Emissivity of any body (e) is always less than its absorptive power (a). Reason : Both the quantities are dimensionless.A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. If Assertion is true, but the Reason is false.D. If Assertion is false but the Reason is true.
• Choose the correct optios.A. Good absorbers of a particular wavelength are good emitters of same wavelength. This statement was given by Kirchhoff.B. At low temperature of a body the rate of cooling is directly proportional to temperature of the body. This statement was given by the NewtonC. Emissive power of a perfectly black body is 1D. Absorptive power of a perfectly black body is 1