HARD
JEE Advanced
IMPORTANT
Earn 100

Three charged particles are in equilibrium under their electrostatic forces only.
(a)The particles must be collinear.
(b)All the charges cannot have the same magnitude.
(c)All the charges cannot have the same sign.
(d)The equilibrium is unstable.

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Important Questions on Coulomb's Law and Electric Field
HARD
JEE Advanced
IMPORTANT
A simple pendulum of mass charged negatively to coulomb oscillates with a time period in a downward electric field such that If the electric field is withdrawn, the new time period


MEDIUM
JEE Advanced
IMPORTANT
Two objects and are charged. Let charge on and charge on , then match column I and column II.
Column I | Column II | ||
---|---|---|---|
(i) | a. | Charge transfer by conduction | |
(ii) | b. | Charging by friction | |
(iii) | c. | Charging by induction |

HARD
JEE Advanced
IMPORTANT
Let and are two identical objects of same mass initially are charged electrostatically by rubbing against each other. Let has got a positive charge and has got a negative charge, then match column I and column II.
Column I | Column II | ||
---|---|---|---|
(i) | Mass of | a. | Increases |
(ii) | Mass of | b. | Decreases |
(iii) | Work function of | c. | Is less |
(iv) | Work function of | d. | Is more |

HARD
JEE Advanced
IMPORTANT
Two concentric rings, one of radius and the other of radius , have the charges , and , respectively, as shown in the figure. Find the ratio if a charged particle placed on the axis at is in equilibrium


HARD
JEE Advanced
IMPORTANT
A rod of length and mass is uniformly charged with a charge , and it is suspended from the end as shown in the figure. The rod can freely rotate about in the plane of the figure. An electric field is suddenly switched on in the horizontal direction due to which the rod gets turned by a maximum angle of . The magnitude of is equal to . Find the value of .


HARD
JEE Advanced
IMPORTANT
Four charged particles each having charge are fixed at the corners of the base ( and ) of a square pyramid with slant length , a charge is fixed at point . A dipole with dipole moment is placed at the centre of the base and perpendicular to its plane as shown in figure. Force on the dipole due to the charge particles is . Find the value of ?

HARD
JEE Advanced
IMPORTANT
A ring of radius has charge distributed uniformly over it. calculate the charge that should be placed at the center of the ring such that the electric field becomes zero at a point on the axis of the ring distant from the center of the ring. The value of is . Find the value of

HARD
JEE Advanced
IMPORTANT
Two identical small equally charged conducting balls are suspended from long threads secured at one point. The charges and masses of the balls are such that they are in equilibrium when the distance between them is (the length of the thread ). One of the balls is then discharged. Again for the certain value of distance between the balls, the equilibrium is restored. Find the value of .
