Tag: electrostatics

Questions Related to electrostatics

Two identical balls each having mass density $ \rho _1 $ mass m and charge q are suspended from a common point by two insulating massless strings of angle $\theta$ with the vertical. Now both the ball are immersed in a liquid.At equilibrium, $ \theta $ remain same. If the mass density of liquid is $ \sigma  $ then dielectric constant of liquid will be

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. $ \frac {\sigma }{\rho - \sigma } $

  2. $ \frac {\rho }{\rho - \sigma } $

  3. $ \frac {\sigma }{\rho } $

  4. $ \frac {\rho }{ \sigma } $

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Correct Option: A

Two charges when kept at a distance of $1 m$ apart in vacuum have some force of repulsion. If the force of repulsion between these two charges be same, when placed in an oil of dielectric constant $4$, the distance of separation is 

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. $0.25m$

  2. $0.4m$

  3. $0.5m$

  4. $0.6m$

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Correct Option: A

The induced charge on the dielectric of a capacitor of capacitance $4\mu F$ when charged by a battery of $50$V, is (dielectric constant of the dielectric $=4$):

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. $100\mu C$

  2. $200\mu C$

  3. $50\mu C$

  4. $150\mu C$

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Correct Option: D

When a metal plate is introduced between the two plates of a charged capacitor and insulated from them, then

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. the metal plate divides the capacitor into two capacitors connected in parallel to each other

  2. the metal plate divides the capacitor into two capacitors connected in series with each other

  3. the metal plate is equivalent to a dielectric of zero dielectric constant

  4. the metal plate is equivalent to a dielectric of infinite dielectric constant

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Correct Option: B,D
Explanation:

The capacitor is divided into two capacitors joined in series. So (b) is correct. Also as K for a metal is $\infty$, therefore (d) is also correct.

A charge is placed at some distance from a non uniform conductor . Now charge is slowly moved towards the conductor at a slow rate ,now which of the following is correct regarding it,

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. surface charge density increases

  2. surface charge density decreases

  3. more charge is accumulated inside the conductor because of higher electric field.

  4. force is required to maintain the constant rate of movement of charge towards the conductor.

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Correct Option: A,D

On the application of electric field on a dielectric and a conductor one by one which of the following is observed

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. electric field inside the conductor is more as compared to dielectric.

  2. electric charge on the surface of conductor is more as compared to dielectric.

  3. electric potential energy entrapped in dielectric is more as compared to conductor .

  4. dielectric breakdown (if produced ) may allow the dielectric to function as a conductor with respect to flow of current.

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Correct Option: B,D

Which of the following statement is correct regarding dielectric?

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. Dielectric constant is the numerical value which signifies the extent of electric field decreased passing through it.

  2. Conductor can be considered as dielectric having dielectric constant as infinite

  3. The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space.

  4. None of the above

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Correct Option: A,B,C

Which of the material can be used as a dielectric?

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. Ceramics

  2. Wood

  3. Copper

  4. Aluminium

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Correct Option: A,B
Explanation:

we know that only non conductor can be used as a dilectric.So only A and B are correct option.

Dielectric constant, property of an electrical insulating material (a dielectric) equal to

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. the ratio of the capacitance of a capacitor filled with the given material to the capacitance of an identical capacitor in a vacuum without the dielectric material.

  2. the ratio of the capacitance of a capacitor filled with the given material to the capacitance of an identical capacitor in a vacuum with the dielectric material.

  3. the capacitance of a capacitor filled with the given material 

  4. none  of the above 

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Correct Option: A
Explanation:

The capacitance of a parallel plate capacitor filled with the given material of dielectric constant $K$ is given by:

              $C=\dfrac{K\varepsilon _{0}A}{d}$ .....................eq1
And the capacitance of the same capacitor without the given material is given by:
              $C'=\dfrac{\varepsilon _{0}A}{d}$  .....................eq2
Dividing eq1 by eq2,
              $C/C'=K$

Which of the following can be used as dielectric?

dielectric substances and polarization dielectrics and polarisation electrostatic potential and capacitance electrostatics physics

  1. Mineral oil

  2. Electrets

  3. Sulfur hexafluoride

  4. None of the above

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Correct Option: A,B,C
Explanation:

We know that dielectric is a medium or substance with a dielectric property; an insulator.So, from the option Mineral oil,Electrets and also Sulfur hexafluoride can be used as dilectric.

Therefore, A,B and C are correct option.