NEET UG Physics Electrostatics MCQs

28. When a metallic conductor is placed in an external electric field,
(i) A stationary charge distribution is induced on the surface of the conductor.
(ii) The resultant electric field inside the conductor is zero.
(ii) The net electric charge inside the conductor is zero.
(iv) The electric field at every point on the outer surface of conductor is locally normal to the surface.
(v) The electric potential inside the region of conductor is the same every where.
(vi) If there is a cavity in the conductor then, even when the conductor is placed in an external electric field, the resultant electric field inside the conductor and also inside the cavity is always zero.

This fact is called the electrostatic shielding.

103. The capacitors of capacitance 4μF, 6μF and 12μF are connected first in series and then in parallel. What is the ratio of equivalent capacitance in the two cases ?
(A) 2 : 3 (B) 11 : 1 (C) 1 : 11 (D) 1 : 3

104. Large number of capactors of rating 10μF/200V V are available. The minimum number of capacitors required to design a 10μF/700V capacitor is
(A) 16 (B) 8 (C) 4 (D)7

105. A variable condenser is permanently connected to a 100 V battery. If capacitor is changed from 2μF to 10μF . then energy changes is equal to
(A) 2×10^–2J (B) 2.5×10^–2J (C) 6.5×10^–2J (D) 4×10^–2J

106. Two positive point charges of 12μc and 8μc are placed 10 cm apart in air. The work done to bring them 4 cm closer is
(A) Zero (B) 4.8 J (C) 3.5 J (D) 5.8 J

107. 1000 similar electrified rain drops merge together into one drop so that their total charge remains unchanged. How is the electric energy affected ?
(A) 100 times (B) 200 times (C) 400 times (D) 102 times

108. There are 10 condensers each of capacity 5μF. The ratio between maximum and minimum capacities obtained from these condensers will be
(A) 40 : 1 (B) 25 : 5 (C) 60 : 3 (D) 100 : 1

109. A parallel plate capacitor is made by stocking n equally spaced plates connected alternately.
If the capacitance between any two plates is x, then the total capacitance is,
(A) nx (B) nx² (C) n/x (D) (n – 1)x

139. An electric circuit requires a total capacitance of 2μF across a potencial of 1000 V. Large number of 1μF capacitances are available each of which would breakdown if the potential is more then 350 V. How many capacitances are required to make the circuit ?
(A) 24 (B) 12 (C) 20 (D) 18

140. Read the assertion and reason carefully to mark the correct option out of the options given below :
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

3. Assertion : A metalic shield in form of a hollow shell may be built to block an electric field.
    Reason : In a hollow shherical shield, the electric field inside it is zero at every point.

4. Assertion : Electrons move away from a low potential to high potential region.
    Reason : Because electrons have negative charge

5. Assertion : If the distance between parallel plates of a capacitor is halved and dielectric constant is made three times, then the capacitance becomes 6 times.
    Reason : Capacity of the capacitor does not depend upon the nature of the material.

6. Assertion : A parallel plate capacitor is connected across battery through a key. A dielectric slab of constant K is introduced between the plates. The energy which is stored
                       becomes K times.
    Reason : The surface density of charge on the plate remains constant or unchanged.

7. Assertion : Electric lines of force cross each other.
    Reason : Electric field at a point superimpose to give one resultant electric field.

8. Assertion : If a proton and an electron are placed in the same uniform electric field. They experience different acceleration.
    Reason : Electric force on a test charge is independent of its mass.

9. Assertion : Dielectric breakdown occrus under the influence of an intense light beam.
    Reason : Electromagnetic radiations exert pressure.

10. Assertion : When charges are shared between any two bodies, no charge is really lost, but some loss of energy does occur.
      Reason : Some energy disappeares in the form of heat, sparking etc.