# Uttar Pradesh PSC Exam: Physics MCQs (Practice_Test 15 of 35)

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- Maxwell՚s thermodynamic relations connect coordinate derivatives evaluated at
- two different equilibrium positions along a single reversible path
- two equilibrium positions along two different reversible paths
- a single equilibrium positions along two different reversible paths
- a single equilibrium position along one reversible path

- The volume of a certain mass of gas at constant pressure is doubled to its value at 00C. The temperature of the gas will be
- 1000C
- 1730C
- 2730C
- 5460C

- The period of oscillations of a galvanometer mirror due to the Brownian motion is 40 s. The moment of inertia of the galvanometer about its suspension axis is 8 × 10 − 12kg-m2. The root-mean-square of maximum deflection of this mirror at a temperature of 500C, is
- 2.7 × 10 − 4 rad
- 2.1 × 10 − 4rad
- 1.5 × 10 − 4rad
- 0.9 × 10 − 4rad

- In the porous plug experiment, the temperature of the gas increases after throttling. The correct range for the initial temperature of the gas for this to happen is
- boiling temperature to critical temperature
- critical temperature to Boyle՚s temperature
- Boyle՚s temperature to inversion temperature
- below inversion temperature

- If a black body radiation in a spherical cavity of volume V satisfies the relation PVh = constant during a quasi-static isentropic process, then the numerical value of h should be
- A long straight vertical wire carries a current of 10A directed upwards. If the horizontal component of the earth՚s magnetic field at the plane is 2 × 10 − 5 T, then the distance of the point from the wire at which the net B is zero, is
- 0.05m
- 0.10m
- (0.05) pm
- (0.1) pm

- A wire bent into the form of an ellipse has semilatus rectum L and eccentricity a. For a current I in the wire, the magnetic field at one of the foci of the ellipse will be
- m0I/2L
- m0I/L
- ma0I/2L
- ma0I/L

- If the B-H curves of two samples of P and Q of iron are as shown above, then which one of the following statements is correct?
- Both P and Q are suitable for matching permanent magnets
- P is suitable for making permanent magnets and Q for matching electromagnets
- P is suitable for making electromagnets and Q is suitable for permanent magnets
- Both P and Q are suitable for making electromagnets

- One billion electrons are placed on a solid copper sphere. If this system attains equilibrium, then the electrons will be
- uniformly distributed on the surface of the sphere
- uniformly distributed in the interior of the sphere
- concentrated at the centre of the sphere
- concentrated at the bottom of the sphere

- If two infinite oppositely charged plates with surface charge density I s I on each plate are kep perpendicular to each other as shown in the above figure, then a charge q at p will experience a force
- sq/20 away towards the vertical plate
- sq/20 away from the horizontal plate
- sq/rt20 towards the origin, 0
- sq/rt20 making 450 with respect to the vertical direction

- The above figure shows electric field E at distance r in any direction from the origin O. The electric field E is due to
- a charged hollow metallic sphere of radius OP with centre at O
- a charged solid metallic sphere of radius OP with centre at O
- a uniformly charged non-conducting sphere of radius OP with centre at O
- a uniformly charged non-conducting hollow sphere radius OP with centre at O

- The capacitance of a parallel plate capacitor is 2 × 10 − 6 F. It changes to 2 × 10 − 6 F when a dielectric is inserted between the plates. The relative permitivity of the dielectric is
- 20
- 2
- 1

- A parallel plate capacitor has an electric field of 10s V/M between the plates. If the charge on the capacitor plate is 1 mc, then the force on each capacitor plate is
- 0.1 N
- 0.05 N
- 0.02 N
- 0.01 N.

- In the circuit shown in the above figure, the resultant resistance between P and Q is
- 5 W
- 14W
- 15W
- 20W

- A conductor wire, having 1Q29 free electrons per m3 carries a current of 20 A. If the cross-section of wire is 1 mm2 then the drift velocity of electrons will be of the order of
- 10 − 5 m/s
- 10 − 3 m/s
- 10 − 1 m/s
- 10 ms