ElectroStats

One metallic sphere A is given positive charge whereas another identical metallic sphere B of exactly same mass as of A is given equal amount of negative charge. Then,

• Mass of A and mass of B still remain equal

• Mass of A increases

• Mass of B decreases

• Mass of B increases

Two point charges A and B, having charges +Q and –Q respectively, are placed at certain distance apart and force acting between them is F. If 25% charge of A is transferred to B, then force between the charges become

• 9F/16

• 16F/9

• 4F/3

• F

Two identical charged spheres suspended from a common point by two massless strings of lengths l, are initially at a distance d (d << l) apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity v. Then, v varies as a faction of the distance x between the sphere, as

• A

• B

• C

• D

Two positive ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be (e being the charge on an electron)

• A

• B

• C

• D

Read the Question In Image and mark A/B/C/D as given against each option

• A

• B

• C

• D

A charge q is placed at the centre of the line joining two exactly equal positive charges Q. The system of three charges will be in equilibrium, if q is equal to  

• – Q/4

• +Q

• –Q

• Q/2

An electric dipole, consisting of two opposite charges of 2×10^(-6) C each separated by a distance 3 cm is placed in an electric field of 2×10^5  N/C. Torque on the dipole is

• 12 × 10–1 N-m

• 12 × 10–2 N-m

• 12 × 10–3 N-m

• 12 × 10–4 N-m

Three point charge +q,-2q and +q are placed at point (x=0,y=a,z=0), (x=0,y=0,z=0) and (x=a,y=0,z=0), respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are:

• √2  qa along +y direction

• √2  qa along the line joining point (x=0,y=0,z=0) and (x=a,y=a,z=0)

• qa along the line joining points (x=0,y=0,z=0) and (x=a,y=a,z=0)

• √2  qa along +x direction

An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is               [NEET 2018]

• 10 times greater

• smaller

• 5 time greater

• equal

A charged wire is bent in the form of a semicircular arc of radius a. If charge per unit length is λ coulomb/metre, the electric field at the centre O is

• A

• B

• C

• D