Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NTA Abhyas JEE Main2020PhysicsElectrostaticsPractice

A neutral sphere of radius r and density ρ is intended to be suspended with an electric field E existing on the earth's surface directed vertically up. What fraction of the electrons should be removed from the sphere? Given that, the atomic number and atomic mass of the material of the sphere are Z and A respectively. Avogadro number is N A . Assume that the sphere is able to hold the necessary charge without any lea

Options

  1. A2 g e E Z A N A
  2. B3 g A e E Z
  3. Cg A e E Z N A
  4. D2 g A e E Z N A

Correct answer

C. g A e E Z N A

Step-by-step solution

m g   =   q E ⇒   m g   =   n e E ⇒   4 3 π r 3   × ρ   ×   g   =   n e E n   =   4 π r 3 ρ g 3 e E N u m b e r   o f   m o l e s   o f   t h e   m e t a l   i n   s p h e r e =   m A =   4 3 π r 3 ρ A N u m b e r   o f   m e t a l   a t o m s =   4 3 π r 3 ρ × N A A T o t a l   n u m b e r   o f   e l e c

Practice Electrostatics on Quantrex Academy →

More from Electrostatics

Two charges Q₁ = q and Q₂ = mq are placed at the points P₁(a, b) and P₂(ma, mb) , respectively, in the XY plane, where a, b 0 and m 0, 1 . If V₁ is the potential at a point in the 2026Consider an electric dipole comprising two charges +q and -q each with mass m , separated by a fixed distance d and initially at rest with its dipole moment pointing along i . A un 2026Two point charges q₁=3 , C and q₂=-4 , C are placed at points (2 i +3 j +3 k ) and ( i + j + k ) respectively. Force on charge q₂ is ________ N. ( Take 1 4 ₀ = 9 10^9 SI Units ) 2026The electric potential as a function of x, y is given by V = 5(x^2 - y^2) V. The electric field at a point (2, 3) m is __________ V/m. 2026A thin half ring of radius 35 cm is uniformly charged with a total charge of Q coulomb. If the magnitude of the electric field at centre of the half ring is 100 V/m, then the value 2026A three coulomb charge moves from the point (0, -2, -5) to the point (5, 1, 2) in an electric field expressed as E = 2x i + 3y^2 j + 4 k N/C. The work done in moving the charge is 2026A particle of charge q and mass m is projected from origin with an initial velocity v = ( v₀ 2 x + v₀ 2 y ) . There exists a uniform magnetic field B = B₀ z and a space varying ele 2026A rigid dipole undergoes a simple harmonic motion about its centre in the presence of an electric field E ₁=E₀ x . If another electric field E ₂=2E₀( y + z ) is introduced to the s 2026 Full Electrostatics list All NTA Abhyas JEE Main PYQs