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Questions and Answers
What determines the extent of polarization in a dielectric material?
What determines the extent of polarization in a dielectric material?
- The type of external field applied
- The temperature of the dielectric material only
- The relative strength of dipole potential energy and thermal energy (correct)
- The size of the dielectric slab
What is the term used to describe the dipole moment per unit volume in a dielectric?
What is the term used to describe the dipole moment per unit volume in a dielectric?
- Dielectric constant
- Susceptibility
- Polarization (correct)
- Temperature coefficient
In the equation P = ε0 χe E, what does χe represent?
In the equation P = ε0 χe E, what does χe represent?
- Total charge density
- Electric susceptibility of the dielectric medium (correct)
- Molecular dipole strength
- Electric field strength
What happens to the positive and negative charges in a dielectric when it is subjected to an external field?
What happens to the positive and negative charges in a dielectric when it is subjected to an external field?
What factor tends to disrupt the alignment of dipoles in a dielectric material?
What factor tends to disrupt the alignment of dipoles in a dielectric material?
What is the result of applying a uniform external field to a dielectric slab?
What is the result of applying a uniform external field to a dielectric slab?
Which statement is true regarding the internal field of a polarized dielectric?
Which statement is true regarding the internal field of a polarized dielectric?
What occurs at the surfaces of a dielectric when it is polarized in an external electric field?
What occurs at the surfaces of a dielectric when it is polarized in an external electric field?
What happens to the work done by an external force when moving charge q from point R to point P?
What happens to the work done by an external force when moving charge q from point R to point P?
What does the potential energy difference $ riangle U$ represent?
What does the potential energy difference $ riangle U$ represent?
When the external force is removed after reaching point P, what does the electric force do?
When the external force is removed after reaching point P, what does the electric force do?
Which of the following statements is true regarding the direction of work done by the electric field?
Which of the following statements is true regarding the direction of work done by the electric field?
How does the potential energy at point P relate to the work done moving charge q from R to P?
How does the potential energy at point P relate to the work done moving charge q from R to P?
What influences the value of the potential energy difference $ riangle U$?
What influences the value of the potential energy difference $ riangle U$?
Why is the work done by electric force considered negative in this context?
Why is the work done by electric force considered negative in this context?
If charge q is moved with constant speed, what can be said about the net force acting on it during the process?
If charge q is moved with constant speed, what can be said about the net force acting on it during the process?
What is the total dipole moment of all the molecules in the substance when the dipole moment of each molecule is $10^{-29}$ C m?
What is the total dipole moment of all the molecules in the substance when the dipole moment of each molecule is $10^{-29}$ C m?
What is the initial potential energy (Ui) when $q = 0°$?
What is the initial potential energy (Ui) when $q = 0°$?
What is the formula for the electrostatic potential V at a distance r from a point charge Q?
What is the formula for the electrostatic potential V at a distance r from a point charge Q?
For a negative charge Q, how does the work done by the external force compare when a positive test charge is brought from infinity to a point P?
For a negative charge Q, how does the work done by the external force compare when a positive test charge is brought from infinity to a point P?
What does the change in potential energy indicate when dipoles align with a new electric field direction?
What does the change in potential energy indicate when dipoles align with a new electric field direction?
What happens to the electrostatic field inside a conductor?
What happens to the electrostatic field inside a conductor?
What does it imply if the electrostatic potential V is negative when Q < 0?
What does it imply if the electrostatic potential V is negative when Q < 0?
In metallic conductors, which charged particles are primarily responsible for conducting electricity?
In metallic conductors, which charged particles are primarily responsible for conducting electricity?
How does the electrostatic potential vary with distance r from a point charge?
How does the electrostatic potential vary with distance r from a point charge?
What is the final potential energy (Uf) when the dipoles align at an angle of $60°$?
What is the final potential energy (Uf) when the dipoles align at an angle of $60°$?
What happens to the work done in bringing a charge from infinity to point P if the charge Q is doubled?
What happens to the work done in bringing a charge from infinity to point P if the charge Q is doubled?
Which of the following correctly describes the relationship between electrostatic force and displacement when bringing a positive charge to a point P near a negative charge?
Which of the following correctly describes the relationship between electrostatic force and displacement when bringing a positive charge to a point P near a negative charge?
In the context of electrolytic conductors, what adds complexity to the movement of charge carriers?
In the context of electrolytic conductors, what adds complexity to the movement of charge carriers?
When switching the direction of an external electric field by 60º, what is the energy released during the alignment of dipoles?
When switching the direction of an external electric field by 60º, what is the energy released during the alignment of dipoles?
What is the implication of considering the potential at infinity to be zero?
What is the implication of considering the potential at infinity to be zero?
When integrating to find the potential due to a point charge, which variable is used in the limits of integration?
When integrating to find the potential due to a point charge, which variable is used in the limits of integration?
What does the electrostatic potential (V) at a point represent?
What does the electrostatic potential (V) at a point represent?
When calculating the work done per unit test charge, which quantity is used as an infinitesimal change?
When calculating the work done per unit test charge, which quantity is used as an infinitesimal change?
How does the work done by an external force depend on the electrostatic field?
How does the work done by an external force depend on the electrostatic field?
What is assumed about the charge Q when determining the potential at point P?
What is assumed about the charge Q when determining the potential at point P?
What does the work done in bringing a unit positive test charge from infinity indicate about the electrostatic potential?
What does the work done in bringing a unit positive test charge from infinity indicate about the electrostatic potential?
What is the significance of choosing the potential to be zero at infinity?
What is the significance of choosing the potential to be zero at infinity?
Why is it important to consider the electrostatic force acting on a test charge when determining potential?
Why is it important to consider the electrostatic force acting on a test charge when determining potential?
What is implied about the potential difference in regions with electrostatic fields?
What is implied about the potential difference in regions with electrostatic fields?
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Study Notes
Work done by external forces
- Work done by external forces in moving a charge q from R to P is equal to the negative of the work done by the electric force.
- This work done is stored as potential energy.
- Potential energy difference between two points is defined as the work required to be done by an external force in moving charge q from one point to another.
Electrostatic potential
- Electrostatic potential (V) at any point in a region with electrostatic field is the work done in bringing a unit positive charge from infinity to that point.
- The potential at infinity is zero.
Potential due to a point charge
- The potential at point P due to a charge Q at the origin is given by: V(r) = Q/(4πε₀r).
- The potential is positive for a positive charge Q and negative for a negative charge Q.
- The variation of potential V with r is proportional to 1/r.
Electrostatics of conductors
- Conductors contain mobile charge carriers. In metallic conductors, these charge carriers are electrons.
- Inside a conductor, electrostatic field is zero.
- The free electrons in a conductor move randomly in different directions.
- In an external electric field, the electrons drift against the direction of the field.
Dielectrics
- The extent of polarisation of a dielectric depends on the dipole potential energy in the external field and thermal energy.
- The dipole moment per unit volume is called polarisation and is denoted by P.
- For linear isotropic dielectrics, P = ε₀ χe E, where χe is the electric susceptibility of the dielectric medium.
- The polarized dielectric modifies the original external field inside it.
- At the surfaces of the dielectric normal to the electric field, there is a net charge density.
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