UPSC General Science:Sound and Other Mechanics-1

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Today’s Topic :Sound and Other Mechanics-1

1. Which one of the following is correct about consequent pole:

a) It is pole of magnet which gets weaker due to demagnetisation.

b) IT is a pole developed due to faulty magnetisation.

c) It is a the pole created by magnetisation through inducting

d) It is the pole of paramagnetic sub stances.

Ans:     B

Explanation:    Due to faulty magnetisation, a magnet is sometimes found to have developed more than two poles. For example, in the method of divided touch, if both the strikers poles are north poles, then the steel bar will developed south poles at the two end with the north pole at the middle. The extra pole that is developed at the middle is known as consequent pole.

2. Centre of the sphere would be:

a) Same as at a point 5 cm away from the surface b) Zero

c) Same as the point 25 cm away from the surface d) None of these

Ans:    D

Explanation:    In the case of hollow sphere, the potential at any point inside the sphere is equal to the potential on its surface. As the potential on the surface is 10V, there fore potential at the centre of the sphere would be also 10V.

3. Consider the following statements and select correct code:

1) The amount of current flowing through the circuit decreases by increasing the turns of wire rheostats.

2) The Rheostats are used for increasing or decreasing the strength of a current in a circuit. Codes:

a) Only 2 is correct                                b) Neither one now two correct

c) Both 1 and 2 are correct                   d) Only 1 is correct.

Ans:     C

Explanation:    Since the electric resistance of a material is dependent on its length, more the turns of wire on the rheostats, greater is its resistance and smaller the amount of current that flow through the circuit. So code(c) is correct.

4. Consider the following statements and select correct codes:

1) When external magnetic field is applied to diamagnetic substances, the field inside the substance is slightly weakened and the substances possessed a minute magnetic effect.

2) Paramagnetic substances contain equal number of electron spinning is opposite direction.

a) 1 and 2 are correct                   b) Only 2 is correct

c) Only 1 is correct                       d) Neither one (1) nor 2 are correct.

Ans:     B

Explanation:    Diamagnetic substances contain equal number of electron spinning is opposite direction. These electron neutralize the magnetic force of each other, but when an external magnetic field is applied their orbit slightly disturbed.

5. Which one of the following acts as a defect of simple cell:

a) Polarisation                   b) Oxidisation                   c) Local action                         d) A and C

Ans:     D

Explanation:    Polarisation is the deposition of hydrogen bubbles on the copper plate in simple cell which continuously weaken the main current and after sometime the current stops flowing. Local action occur because of the use of commercial zinc as metallic impurities contained only impure zinc acts a positive plates and small local cells are formed on the zinc plate.

6. The amplification factor of a triode value depend upon which one of the following:

a) relative position of cathode, grid and plate.

b) Plate voltage

c) Temperature of the cathode

d) temperature of the plate.

Ans:     B

Explanation:    Here M           = Rp x gm

Where Rp is the plate resistance and gm is the mutual conductance. Hence the amplification factor of a triode value depend upon the plate resistance.

7. The orbital velocity of an earth’s artificial satellite sift it revolving near the earth’s surface would be which of the following:

a) 5.98 km/s                   b) 11.20 km/s c) 7.92 km/s                 d) 20.50 km/s

Ans:     C

Explanation:    Here

V = ,

g = 9.8m/s2 and R = 6.4 x 106 m

V = 7.92 x 103 m/s

V = 7.92 km/s

8. The energy generation in star is due to which one of the following:

a) Chemical reaction                      b) Fustian of heavy nuclei

c) Fusion of light nuclei                   d) None of these.

Ans:     C

Explanation:    The energy of generation in the stars is due to fusion of nuclei into a heavy nucleus. The mass of a single nucleus is less than the initial mass. The differences in mass are converted into energy of stars.

9. The radio station broadcast at 30 meter band. The frequency of electromagnetic waves transmitted from the station could be:

a) 19 x 1011HZ                   b) 18 x 109 HZ                   c) 10 MHZ       d) 4 x 1010 MHZ

Ans:     C

Explanation:    We know that

V = C/X

V =

V = 107

V = 10 MHZ.

10. Which one of the following would fill the empty sapce in the given below nuclear reaction:

a) Alpha particle                   b) Proton

c) Neutron                           d) None of these.

Ans:     C

Explanation:    5B10 + 2He4 + 7N13 + 0X1

as Z = 0 and A = 1 ,  0 X1 = 0H1, So it is a neutron.