Electric charges and fields class 12 questions with answers


ELECTRIC CHARGES AND FIELDS

Focus to be on the topics
  • Electric charges and its properties
  • The intensity of Electric field
  • Electric dipole
  • Gauss law and its applications
1 MARK QUESTIONS
  1. Write any two properties of electric charges.
  2. State Coulomb's law of force between charges at rest.
  3. Define the dielectric constant.
  4. Give the SI unit of electric permittivity of free space.
  5. Define linear charge density and give its SI units.
  6. Define the electric field at a point in an electric field.
  7. What is an electric dipole?
  8. When is the torque on a dipole in an electric field maximum?
  9. Define electric flux.
  10. Is electric dipole moment a scalar or vector?
  11. Define Gauss law.
  12. What is the intensity of the electric field at a point inside the charged spherical shell?
  13. Write SI units for the intensity of the electric field.
  14. What is the effect of medium on the force between two point charges at a fixed distance?
  15. What is the least possible value of charge?
           Answers
  1. Electric charge properties 1) Scalar  2) Quantised  3) Conserved  and 4) additive  (You can write any two properties)
  2. The force of attraction or repulsion between any two point charges at rest is directly proportional to the product of the magnitude of charges and inversely proportional to the distance between them.
  3. It is the ratio between permittivity of the medium to the permittivity of the free space  (or)  It is the ratio between force between two charges at a fixed distance in free space/air to the force between two charges in the medium.
  4.  C2/Nm2    or coulomb2/newton meter2   
  5. Charge per unit length. Unit - C/m.
  6. The intensity of the electric field at a point in the electric field is the force experienced by a unit positive charge placed at that point.
  7. An electric dipole is a system of two charges identical in magnitude but opposite in sign separated by a fixed distance.
  8. If the angle between electric dipole moment and intensity of electric fields are right angles to each other then torque on the dipole will be maximum.
  9. Electric flux nothing but the number of electric lines of force.
  10. The electric dipole moment is a vector directed from a negative charge to a positive charge.
  11. The total normal flux through the entire closed surface is equal to the 1/ɛ0 times the charge enclosed by the surface.
  12. Zero (Why because there is no charge inside the shell)
  13. E = F/q  so unit  N/C.
  14. Due to the medium force between the charges decreases.
  15. The least possible value of the charge is electron charge i.e. 1.6 x 10-19 coulomb.


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