Electrostatics Important Five mark questions with answers for CBSE Class 12 (previous year)

Electrostatics Five mark questions for CBSE Class 12 (previous year )

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Electrostatics Important Five mark questions for CBSE Class 12 (previous year )

1. a. Derive an expression for the energy stored in a parallel plate capacitor C , charged to a potential difference V.
   b. Obtain the capacitance of the network given below . For a supply of 300 V , determine the charge and voltage across C₄ .
   
   
   Electrostatics Important Five mark questions with answers for CBSE Class 12 (previous year)
   [2008]
   
   
2. Explain the principle of a device that build up high voltages of the order of a few million volts . Draw a schematic diagram and explain the working of this device . Is there any restriction on the upper limit of high voltage set up in this machine ? Explain .
   
   [CBSE 2012]
   Or
   

   a. Define electric flux. Write the S.I. units .
   b. Using Gauss law , prove that the electric field at a point due to a uniformly charged infinite plane sheet is independent of the distance from it .
   c. How is the field directed if
   i.) sheet is positively charged  ii.) Sheet is negatively charged
3. a. Define electric dipole moment . Is it scalar or vector ? Derive the expression for the electric field of a dipole at a point on the equatorial plane of the dipole.
   b. Draw the equipotential surfaces due to an electric dipole . Locate the points where the potential due to dipole is zero .
   
   

   [CBSE 2013]

   
   

   Or
   
   

   Using Gauss law deduce the expression for the electric field due to a uniformly charged spherical conducting shell of the radius R at a point i.) outside and ii.) inside the shell
   Plot a graph showing variation of electric field as a function of r > R and r < R ( r being the distance from the center of the shell )
4. Draw a labelled diagram of Van de Graff generator . State its working principle  to show how by introducing a small charged sphere into a larger sphere , a large amount of charge can be transferred to the outer sphere . State the use of this machine and also point out its limitations.
   
   Or
   

   a. Deduce the expression for the torque acting on a dipole of dipole moment p  in the presence of a uniform electric field E .
   b. Consider two hollow  concentric spheres , S₁ and S₂ , enclosing charges 2Q and 4Q respectively as shown in the figure i.) Find out the ratio of the electric flux through them . ii.)How will the electric flux through the sphere S₁ change if a medium of dielectric constant      ' εr ' is introduced in the space inside S₁ in place of air ? Deduce the necessary expressions .
   
   

   

   
   

   Electrostatics Important Five mark questions with answers for CBSE Class 12 (previous year)
5. a. An electric dipole of dipole moment p consists of point charges +q and -q separated by a distance 2a apart . Deduce the expression for the electric field due to the dipole at a distance x from the centre of the dipole on its axial line in terms of dipole moment p . Hence show that in the limit x >> a , E →2p / (4ᴨϵₒx³)
   b. Given the electric field in the region E = 2x i , find the net electric flux through the cube and the charged enclosed by it .
   
   [CBSE 2015]
   
   

   

   Electrostatics Important Five mark questions with answers for CBSE Class 12 (previous year)
   Or
   

   a. Explain , using suitable diagrams , the difference in the behaviour of the i.) conductor and ii.) dielectric in the presence of external electric field . Define the terms polarisation of a dielectric and write its relation with susceptibility .
   
   b. A thin metallic spherical shell of radius R carries a charge Q on its surface . A point charge Q / 2 is placed at its center C and an another charge +2Q outside the shell at a distance x from the center as shown in the figure . Find i.) the force on charge at the center of shell and at the point A ii.) the electric flux through the shell .
   

   

   Electrostatics Important  Five mark questions with answers for CBSE Class 12 (previous year)

   
   
6. a. Distinguish with the help of a suitable diagram the difference in the behaviour of a conductor and a dielectric placed in an external electric field . How does polarised dielectric modify the original external field ?
   
   

   [A.I. 2016]

   
   b. A capacitor of capacitance C is charged fully by connecting it to a battery of emf E . It is then disconnected from the battery . If the separation between the plates of the capacitor is now doubled , how will the following change ?
   i.) charge stored by the capacitor  ii.) field strength between the plates  iii.) energy stored  by the capacitor
   Justify your answer in each case .
   

   Or
   

   a. Explain why , for any charge configuration , the equipotential surface through a point is normal to the electric field at that point . Draw the sketch of equipotential surfaces due to a single charge ( -q ) depicting the electric field line due to the charge .
   
   b. Obtain an expression for the work done to dissociate the system of three charges placed at the vertices an equilateral triangle of side 'a' as shown below . 

Electrostatics Important  Five mark questions with answers for CBSE Class 12 (previous year)

Answers

These are important five marks questions and answers for electrostatics CBSE Class 12 .

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