In this page we have Short questions on electrostatics for CBSE Board . Hope you like them and do not forget to like , social share
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Question 1
Can we give any amount of charge to a capacitor? Answers
No, on giving charge continuously to a capacitor, the p.d across its plates will go on rising and ultimately the insulation of the medium between the plates will break. Then the capacitor will be discharged giving sparking
Question 2 A capacitor is connected to a battery. If we move its plates further apart, work will be done against the electrostatic attraction between the plates. What will be the effect on the energy of the capacitor? Answers
Since the battery remains connected, the potential difference V between the plates of the capacitor will remain constant.
Now Since Capacitance depends on the distance between the plates, it will decrease with the movement.
Now we know that
Q=CV
Now C is decreasing and V remains constant, the charge will decrease on the capacitor.
Some charges from plates passing through the connecting wire will charge the battery.
Thus some energy of the capacitor will be transferred to the battery. So energy of the capacitor will decrease.
The work done done in moving apart the plates will be used up in this transference and dissipated in the form of heat in the connecting wires
Question 3 two identical metallic spheres A and B of exactly equal masses are taken. Sphere A is given positive charge of Q coulomb and B is given an equal negative charge.So initially before the charge is given
$M_A=M_B=M$
What will be the masses after the charging?
(a) $M_A > M_B$
(b) $M_A < M_B$
(c) $M_A=M_B$
(d) Nothing can be said Answers
The process of giving positive charge involves removal of electrons and that of negative charge involves addition of electrons. Hence the mass of the positively charged sphere will be less than that of negatively charged sphere
Question 4
Two statements
Statement I: A small metallic sphere is placed at the center of a large charged spherical shell and two are the connected by a wire. The charge will not flow from outer sphere to inner sphere
Statement II: A charged conductor is placed inside the hollow conductor and two are connected by the wire. The whole charge will flow on the outer surface of the outer conductor
(a) Both the statement I and II are correct
(b) Statement I is correct only
(c) Statement II is correct only
(d) Both the statement is true Answers
(a)
Question 5
Superposition principle can not be applied to these quantities in electrostatics
(a) Electrostatic energy
(b) Electric Field
(c) Electric Potential
(d) Electric force Answers
(a)
It can be applied to electric Field, electric potential and electric force
Question 6
What is electrostatic Shielding? Answers
The absence of electric field inside the charged conductors means that electric lines of force cannot enter the empty space of any hollow conductor. Thus hollow conductor can be used to acts as electrostatic shield. So sensitive electric instruments can be saved from external electric fields by covering them with hollow conductor.
Question 7
Consider the electric field at the points A, B, C
List the points in increasing order of electric field strength
(a) C> B>A
(b) C>A>B
(c) A>B>C
(d) None of the Answers
(a)
Question 8 Consider the system
Which of the following is true?
(a) Electric flux through surface A2 is zero
(b) Electric Flux through surface A1 is not zero
(c) Electric field at the surface A2 is not zero
(d) None of these Answers
(a),(b) and (c)
Question 9
Two conducting charged spheres X and Y having unequal charges are connected by the wire. Which of the following is true?
(a) Charge is conserved
(b) Electrostatic energy is conserved
(c) Both the charge and electrostatic energy is conserved
(d) Neither of these is conserved Answers
(a)
Question 10
What is true of equipotential surface?
(a) The PD between any two points on the surface is zero
(b) The electric field is always perpendicular to the surface
(c) Equipotential surface are always spherical
(d) No work is done in moving a charge along the surface Answers
(a) (b) and (d)
Question 11
Write down the difference between Electric Motor and Electric generator Answers
Electric Generators
Electric Motors
Device which converts mechanical energy into electrical energy
Device which converts electrical energy into mechanical energy
It is based on Electromagnetic Induction Principle
It is based on moving coil galvanometer
When a closed coil is rotated rapidly in a strong magnetic field ,the magnetic flux through the coil changes continuously .Hence an EMF is induced in the coil and current flows in it in a direction by Fleming right hand rule
When a current is passed through a coil in a magnetic field ,the coil experiences a torque in the direction given by Fleming left hand rule. This torque gives a continuous rotatory motion in the coil in the magnetic field
Two types AC dynamo and DC dynamo
Back Emf is also generated in Motor since it cuts the magnetic flux of the field magnet
Question 12
Define following terms
(a) Dielectric constant of a medium
(b) Electric dipole moment
(c) Electric flux Answers
(a)It is the ratio of the capacitance ($C_0$) of a capacitor with dielectric between the plates to the capacitance ($C_r$) of the same capacitor with vacuum between the plates i.e. $K=\frac {C_r}{C_0}$
(b) It is the product of the magnitude of one of the point charges constitting the dipole ant the distance of separation between two point charges.
(c) Electric flux through an area is the product of the magnitude of the area and the component of electric field vector normal to this area element.
Electric flux = E.ds
SI unit of flux is $NCm^2$
Question 13
Electric field inside a dielectric decreases when it is placed in an external field. Give reason to support this statement. Answers
An electric field EP is induced inside the dielectric in a direction opposite to the direction of external electric field E0. Thus net field becomes
$E=E_0-E_P$
Question 14
Electric field lines can not be discontinuous. Give reason. Answers
Electric field lines can not be discontinous because if they are discontinous then it will indicate the absence of electric field at the break point.
Question 15
Why do electric field lines can never cross each other? Answers
It is so because if they cross each other then at the point of intersection there will be two tangents which is not possible.
Question 16
What is the net amount of charge on a charged capacitor? Answers
The net charge of a charged capacitor is zero because the charges on its two plates are equal in number and opposite in sign. Even when the capacitor is discharged net charge of the capacitor remains zero because then each plate has zero charge.
