Physics - Online Test
Q1. If two electrons are each 1.50× 10-10 m from a proton, as shown in Figure , magnitude of the net electric force they will exert on the proton is
Answer : Option A
Explaination / Solution:
Putting the value of We have
Putting the value of We have
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 point charge Q is moved along a circular path around another fixed point charge The work done is zero
Answer : Option C
Explaination / Solution:
Since that circular path behave as equipotential surface so work done is always zero.
Q4. 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
Q5. In a regular polygon of n sides, each corner is at a distance of r from the center. Identical charges of magnitude Q are placed at (n -1) corners. The field at the center is
Answer : Option D
Explaination / Solution:
If the same charges are placed at all corners on polygon than the electric field at centre will be zero, but in given situation one charge is missing , so the field at the centre now become non zero and the net field at centre must be equal to the field which the missing charge exert such that the total field become zero So now the field at centre=field due to missing charge =
Q6. 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.
Q7. Which of the following is not true for a region with uniform electric field?
Answer : Option B
Explaination / Solution:
In each of the cases given the electric field is not uniform.
Q8. 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
Q9. A charge Q is placed at the mouth of a conical flask. The flux of the electric field through the flask is
Answer : Option A
Explaination / Solution:
If the charge enclosed by conical flask than the flux is
But the charge is placed at the mouth of flask so if we draw another imaginary flask over it the charge is surrounded by two flasks now so the charge through the flask now half of the previous value (shared by two flask) So
Q10. 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.
