Physics Test 56

Result

Physics Test 56

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Question 1
4 / -1

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from

A
The current source

B
The magnetic field

C
The induced electric field due to the changing magnetic field

D
The lattice structure of the material of the rod

Solution

The energy provided by the current source is conserved into gravitational potential energy. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy.

Hence, the correct option is (A).
Question 2
4 / -1

A 100 V source of ac frequency 500 Hz is connected to a series LCR circuit with L=8.1mH C=12.5μF and R=10Ω. Find different capacities across resistance.

A
V = 100 V

B
V = 50 V

C
V = 60 V

D
V = 80 V

Solution
Question 3
4 / -1

A current sheet where current per unit length is 6.0 A/m and direction is towards +i is placed at z=0 in the X-y plane. A current wire is located at y=0 and z=5 m. It is placed along the x axis. Find the current and its direction if Magnetic field is zero at the point P whose location is (0,0,2.5)

A
47 A, i

B
47.1 A, -i

C
50 A, i

D
50 A, -i

Solution

We know that the Magnetic field is independent of the distance for the current sheet. So, Magnetic field at point P,

B₁= 1/2 μ₀K

=3μ₀

The direction will be −j. This can be found by applying the right-hand rule to the few current elements in the sheet Now Magnetic field due to current wire is given by B₂= μ0i / 2πd

B₂= μ0i / 2π2.5

So B₁=B₂

or i=47.1 A

The direction of the current is the wire should be towards i to cancel the magnetic field of the current sheet.

Hence, the correct option is (B).
Question 4
4 / -1

A person is holding a bucket by applying a force of 10 N. He moves a horizontal distance of 5 m and then climbs up a vertical distance of 10 m. Find the total work done by him?

A
100 J

B
150 J

C
50 J

D
200 J

Solution
Question 5
4 / -1

The centre of mass of three particle s of masses 1 kg,2 kg, and 3 kg is at 2,2,2. The position of the fourth mass of 4 kg to be placed in the system so that the new centre of mass is at 0,0,0 is

A
-3, -3, -3

B
-3, 3, -3

C
2, 3, -3

D
2, -2, 3

Solution
Question 6
4 / -1

In which of the following cases is no current induced in the coil with its plane perpendicular to the page as shown in the figure?

A
When the magnet moves towards the coil.

B
When the coil moves towards the magnet.

C
When both move towards each other.

D
When both move in the same direction with the same speed.

Solution

Current is induced in the loop due to electromagnetic induction when the magnetic flux through it changes. When they move with the same speed or velocity, their relative displacement is zero. Therefore, magnetic flux does not change and no current is induced. The direction does not change as it reaches to the same point. Reference can be taken from the figure.

Hence, the correct option is (D).
Question 7
4 / -1

A metal ball immersed in alcohol weight m₁ at 0^∘C and m₂ at 150^∘C. The coefficient of cubical expansion of the metal is less than that of alcohol. Assuming that the density of metal is large as compared to that alcohol it can be shown:

A
m₁ - m₂ > 0

B
m₁ - m₂ < 0

C
m₁ = m₂

D
None of the above

Solution
Question 8
4 / -1

Acceleration due to gravity at earth's surface is g ms⁻². Find the effective value of gravity at a height of 32 km from sea level (R_e=6400 km).

A
0.5g ms⁻²

B
0.99 g ms⁻²

C
1.01g ms⁻²

D
0.90g ms⁻²

Solution
Question 9
4 / -1

Light of two different frequencies whose photons have energies 1eV and 2.5eV respectively, successively illuminate a metallic surface whose work function is 0.5eV. Ratio of maximum speeds of emitted electrons will be

A
1:5

B
3:11

C
1:2

D
1:1

Solution
Question 10
4 / -1

A tank is filled with water of density 1 g / cm³ and oil of density 0.9 g - cm³. The height of water layer is 100 cm and that of oil layer is 400 cm. If g = 980 cm / s², then the velocity of efflux from an opening in the bottom of the tank will be-

A
(952.53) cm/s

B
(940.23) cm/s

C
(949.53) cm/s

D
(939.54) cm/s

Solution