Electrostatic Potential and Capacitance - Online Test
Q1. A parallel plate air filled capacitor shown in Fig. (a) has a capacitance of 2 . When it is half filled with a dielectric of dielectric constant k= 3 as shown in Fig. (b), its capacitance becomes
Answer : Option B
Explaination / Solution:
The capacitance of the first capacitor The second capacitor is considered to be made of two capacitors ( air filled) and ( dielectric) connected in parallel.
Q2. A 2μF capacitor C1 is charged to a voltage 100 V and a 4 μF capacitor C2 is charged to a voltage 50 V. The capacitors are then connected in parallel. What is the loss of energy due to parallel connection?
Answer : Option A
Explaination / Solution:
Explanation here:(A) Initial energy
The common potential after they are connected in parallel
The final energy
The common potential after they are connected in parallel
The final energy
Q3. A parallel plate capacitor of plate area A has a charge Q. The force on each plate of the capacitor is
Answer : Option D
Explaination / Solution:
Force between two plates of the capacitor The energy density The electric field and the charge density
Q4. A capacitor of capacitance C is fully charged by a 200 V supply. It is then discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat and of mass 0.1 kg. If the temperature of the block rises by 0.4 K, what is the value of C?
Answer : Option B
Explaination / Solution:
Energy stored in the capacitor This is released as heat when the capacitor discharges through the metal block. The quantity of heat = mass ×s p.heat× rise in temperature.
Q5. The capacitance of a parallel plate capacitor is 5 μF. When a glass slab of thickness equal to the separation between the plates is introduced between the plates, the potential difference reduces to 1/8 of the original value. The dielectric constant of glass is
Answer : Option A
Explaination / Solution:
When a dielectric of constant K is introduced between the plates of a capacitor, the potential V reduces to V/K. Therefore K=8
Q6. The dielectric constant K of an insulator can be
Answer : Option D
Explaination / Solution:
Dielectric constant of air is 1. All dielectrics generally have a value of the dielectric constant greater than1.where Fm is the force between two charged particles in a medium of dielectric constant K and F is the force between the two charges when placed in air.The force between two charges is greatest in air or vacuum and it decreases when any medium is placed between the charges. K cannot have negative, fractional or zero values.
Q7. If the diameter of earth is , then its capacitance will be
Answer : Option D
Explaination / Solution:
the capacitance of a spherical conductor of radius R is
