Subject

Physics

Class

NEET Class 12

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NEET Physics Solved Question Paper 2012

Multiple Choice Questions

11.
Two conductors having same width and length, thickness d₁ and d₂ thermal conductivity K₁ and K₂ are placed one above the another. Find the equivalent thermal conductivity.

$\frac{(d_{1} + d_{2}) (K_{1} d_{2} + K_{2} d_{1})}{2 (K_{1} + K_{2})}$

$\frac{(d_{1} - d_{2}) (K_{1} d_{2} + K_{2} d_{1})}{2 (K_{1} + K_{2})}$

$\frac{K_{1} d_{1} + K_{2} d_{2}}{d_{1} + d_{2}}$

$\frac{K_{1} + K_{2}}{d_{1_{}} + d_{2}}$

$\frac{K_{1} d_{1} + K_{2} d_{2}}{d_{1} + d_{2}}$

Let t be the width and L be the length of each conductor.

Effective thermal resistance

R = $\frac{R_{1} R_{2}}{R_{1} + R_{2}}$

$∵ R = \frac{L}{KA}$

where k = thermal conductivity

$\frac{L}{A K_{eq}} = \frac{\frac{L}{K_{1} A_{1}} \frac{L}{K_{2} A_{2}}}{\frac{L}{K_{1} A_{1}} + \frac{L}{K_{2} A_{2}}}$

⇒ $\frac{1}{K_{eq} (A_{1} + A_{2})} = \frac{1}{K_{2} A_{2} + K_{1} A_{1}}$

⇒ K_eq = $\frac{K_{1} A_{1}}{A_{1} A_{2}}$

⇒ = $\frac{K_{1} d_{1} t + K_{2} d_{2} t}{d_{1} t + d_{2} t}$

⇒ K_eq = $\frac{K_{1} d_{1} + K_{2} d_{2}}{d_{1} + d_{2}}$

12.

Degree of freedom for polyatomic gas

≥ 4
≥5
≥6
≥7

13.

A particle moving about its equilibrium position with equation y = -ax - bt. interpret the condition

It will always perform SHM
It can never perform the SHM
It can perform SHM only when t ≥ $\frac{bx}{a}$
It can perform SHM only when t ≤ $\frac{bx}{a}$

14.

Conversion of water to steam is accompanied by which process?

Adiabatic
Isothermal
Isochoric
Cyclic

15.

An ideal gas is taken through the cycle A → B → C → A, as shown in figure. If the net heat supplied to the gas in the cycle is 5 J the work done by the gas in the process A → B is

16.

What is the slope for an isothermal process?

$\frac{P}{V}$
$- \frac{P}{V}$
Zero
∞

17.

Assertion: Maximum air flow due to convection does not occur at the north pole but it occurs at 30°N.

Reason: There is maximum temperature difference between equator and 30° N.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

18.

Assertion: Surface energy of an oil drop is same whether placed on glass or water surface.

Reason: Surface energy is dependent only on the properties of oil.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

19.

Assertion: Vibrational energy of diatomic molecule corresponding to each degree of freedom is k_B T.

Reason: For every molecule, vibrational degree of freedom is 2.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

20.

Assertion: Turbulence is always dissipative.

Reason: High reynold number promotes turbulence.

If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.