A capacitor having capacitance 1 uF with air, is filled with

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 Multiple Choice QuestionsMultiple Choice Questions

151.

The capacity of an air condenser is 2.0 µF. If a medium is placed between its plates, the capacity becomes 12 μF. The
dielectric constant of the medium will be

  • 5

  • 4

  • 3

  • 6


152.

Taking the earth to be a spherical conductor of diameter 12.8×103 km. Its capacity will be

  • 711 μF

  • 611 μF

  • 811 μF

  • 511 μF


153.

 A charge Q is distributed uniformly in a sphere (solid). Then, the electric field at any point r,  where, r < R (r is the radius of sphere) varies as:

  • r12

  • -1

  • r

  • -2


154.

As per this diagram a point charge +q is placed at the origin O. Work done in taking another point charge -Q from the point A [coordinates (O, a)] to another point B [coordinates (a, O)] along the straight path AB is

  • zero

  • -qQ4πεo 1a2 2a

  • qQ4πεo 1a2

  • qQ4πεo 1a22a


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155.

A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moments given by

  • q ν R2

  • qνR2

  • q ν R22

  • qνR


156.

A steady current of 1.5 A flows through a copper voltameter for 10 min. If the electrochemical equivalent of copper is 30x 10-5 g C-1 , the mass of copper deposited on the electrode will be

  • 0.40 g

  • 0.50 g

  • 0.67 g

  • 0.27 g


157.

When a charged particle moving with velocity vis subjected to a magnetic field of B induction , the force on it is non- zero. This implies that

  • angle between v and B is necessarily 90o

  • angle between v and B can have any value other than 90o

  • angle between v and B can have any value other than 180o

  • angle between v and B is either zero or 180o


158.

What is not true for equipotential surface for uniform electric field?

  • Equipotential surface is flat

  • Equipotential surface is spherical

  • Electric lines are perpendicular to equipotential surface 

  • Work done is zero


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159.

A capacitor having capacitance 1 uF with air, is filled with two dielectrics as shown. How many times capacitance will increase

              

  • 12

  • 6

  • 8/3

  • 3


B.

6

After filling with dielectrics the two capacitors will be in parallel order. As shown, the two capacitors are connected in parallel. Initially the capacitance of capacitor

                  

                              C = ε0A/d

 

where A is area of each plate and d is the separation between the plates.

After filling with dielectrics, we have two capacitors of capacitance.

Hence, their equivalent capacitance
                               Ceq = C1 + C2 

                                    = 4C +2C 

                               C  = 6C

ie, new capacitance will be six times of the original.



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160.

Figure shows three spherical and equipotential surfaces A, B and C round a point charge q. The potential difference VA - VB = VB -VC If t1 and t2 be the distances between them, then              

  • t1 = t2

  • t1 > t2

  • t1 < t2

  • t1 ≤ t2


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