PGT physics mock test || UP PGT physics free mock test-4

1.The excess pressure inside a bubble of radius R are completely dipped inside the liquid of surface tension S is

1. 2S/r
2. 4S/r
3. 2Sr
4. S/2r

2. If a liquid wets the glass surface the free surface of liquid in the glass capillary will be:

1. Plane
2. Convex
3. Concave
4. All of the above

3. With the rise in temperature the surface tension of a liquid:

1. Increases
2. Decreases
3. Increases or decreases depending upon liquid
4. Doesn't change

4. Two spherical soap bubbles of diameter 10 cm and 6 cm respectively, are formed at the end of a narrow horizontal tube. Pressure difference between the ends of the tube is (surface tension of the soap = 3 x 10^(-2) N/m):

1. 1.6 N.m^(-2)
2. 7.6 N.m^(-2)
3. 11.6 N.m^(-2)
4. 1.1 N.m^(-2)

5. A paper disc of radius R, from which a hole of radius R is cut out, is floating in a liquid of surface tension T, the force on the disc due to surface tension will be:

1. πRT
2. π(R + r)T
3. 2π(R + r)T
4. 4π(R + r)T

6. You are doing an experiment to find surface tension of water by Jaeger's method. If some soap solution is added to the water contained in the beaker, the formula for excess pressure you will use:

1. T/R
2. 2T/R
3. 4T/R
4. T/2R

7. The reason for a raindrop to be spherical in shape is:

1. Viscosity
2. Atmospheric pressure
3. Surface tension
4. Gravitational force

8. Which of the following statements is not correct:

1. Surface tension of a liquid increases with rise in temperature
2. Surface tension of a liquid is independent of the area of the liquid surface
3. A drop of liquid in absence of external forces is always spherical in shape
4. Surface tension helps an insect to crawl on a liquid surface

9. A drop of water is placed between two glass plates to form a thin film of thickness 0.1 mm and area 10 cm square. The force required to pull the plates apart will be:

1. 1 x 10^4 dyne
2. 6 x 10^4 dyne
3. 16 x 10^4 dyne
4. 16 dyne

10. Pressure inside two soap bubbles is 1.01 and 1.03 atmosphere, ratio between their volumes is:

1. 3:1
2. 3:1
3. 27:1
4. 2:3

11. In process of coalescenece of water to drop the surface energy of the system:

1. Decreases
2. Increases
3. Remains unchanged
4. May either decrease or increase

12. The current flowing in a wire of length L is I. It is bent in the form of a circle of One Turn the magnetic field at the centre of this loop is vector B. A circular loop of the same wire is now made having one turn the magnetic field at the centre will now be

1. 2B
2. 3B
3. 4B
4. 4B/3

13. If the velocity of charged particle is doubled and strength of magnetic field is halved then radius becomes

1. 4 times
2. 2 times
3. 8 times
4. 3 times

14. An electron moving with velocity v enters in the magnetic field in the same direction as the direction of magnetic field. The force on the electron is:

1. In the direction opposite to the magnetic field
2. in the direction of magnetic field
3. Zero
4. Perpendicular to magnetic field

15. Two electrons are moving parallel with a velocity v the ratio of magnetic field and electric forces between them will be:

1. constant
2. v/c
3. c/v
4. v

16. The amount of work done in rotating a magnet of moment M through 180 degree from its position along the magnetic meridian is:

1. MB
2. 2MB
3. MB/2
4. 0

17. Which of the following particles will have the maximum frequency of revolution when projected with the same velocity v perpendicular to magnetic field?

1. Lithium ion
2. Helium ion
3. Proton
4. Electron

18.A long solenoid has 200 turns per cm and carries a current of 2.5 A. The magnetic field at its Centre will be (in S.I units):

1. 0.0314
2. 0.0942
3. 0.1256
4. 0.0628

19.A 50 amp current is flowing in a copper wire of diameter 0.005 m. Magnetic field intensity at the surface of wire is:

1. 0.004 gauss
2. 0.04 T
3. 0.004 T
4. 4000 T

20. The expression and magnetic induction inside a solenoid of length L carrying a current I and having N number of turns is:

1. uNI/L
2. 2uNI/L
3. 4unl/L
4. None of the above