Podcast
Questions and Answers
What is the relationship between electric field intensity (E) and potential gradient (dV/dr)?
What is the relationship between electric field intensity (E) and potential gradient (dV/dr)?
Which of the following is a vector quantity?
Which of the following is a vector quantity?
What is the SI unit of electric flux?
What is the SI unit of electric flux?
What is the dimensions of electric potential?
What is the dimensions of electric potential?
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How is the electric field intensity due to a point charge $q$ at distance $r$ given?
How is the electric field intensity due to a point charge $q$ at distance $r$ given?
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What is the value of the permittivity of free space (εo)?
What is the value of the permittivity of free space (εo)?
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Which of the following is correct about the dielectric constant (K) for metals?
Which of the following is correct about the dielectric constant (K) for metals?
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How would the force between two charges change if the medium between them is replaced with a medium of dielectric constant K?
How would the force between two charges change if the medium between them is replaced with a medium of dielectric constant K?
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How do electric field lines behave in the presence of charges?
How do electric field lines behave in the presence of charges?
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How is the force on charge q1 due to charge q2 related to the force on charge q2 due to charge q1?
How is the force on charge q1 due to charge q2 related to the force on charge q2 due to charge q1?
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Study Notes
Coulomb's Law of Electrostatics
- Electrostatic force of interaction between two stationary charges is given by: F = 1 / 4π εo q1q2 / r2
- Permibility of free space (εo) = 8.85 * 10^(-12) C^2 / N-m^2
- Coulomb's law can be used in vacuum or air, for other mediums, εo is replaced by εoK or εoεr, where K is the dielectric constant or relative permittivity of the medium
Coulomb's Law in Vector Form
- Force on q2 due to q1: F12 = q1q2 / 4πε.r1 – r2 / |r1 – r2|^3
- Force on q1 due to q2 = – Force on q2 due to q1 (central forces)
- Electrostatic forces are conservative forces
Electric Field
- Electric field is the space around a charge where its influence can be experienced by other charges
- Electric field lines are imaginary lines or curves that tangent at any point is in the direction of the electric field vector at that point
- Electric field lines never intersect, begin on a positive charge, and end on a negative charge
- Electric field intensity (E) is the electrostatic force per unit positive charge at a point in electric field
- Electric field intensity is a vector quantity, direction is in the direction of electrostatic force acting on positive charge
- Electric field intensity due to a point charge q at a distance r: E = 1 / 4π εo q / r2
Electric Potential
- Electric potential at a point is the work done per positive charge in carrying it from infinity to that point in electric field
- Electric potential, V = W / q
- Electric potential is a scalar quantity
- Electric potential due to a point charge at a distance r: V = 1 / 4π εo q / r
Potential Gradient and Equipotential Surface
- Potential gradient is the rate of change of potential with distance in electric field
- Potential gradient = dV / dr
- Relation between potential gradient and electric field intensity: E = – (dV / dr)
- Equipotential surface is an imaginary surface joining points of same potential in an electric field
- Electric lines of force at each point of an equipotential surface are normal to the surface
Electric Flux
- Electric flux over an area is the total number of electric field lines crossing that area
- Electric flux through a small area element dS: φE = E.dS
- SI unit of electric flux: N – m^2/C
- Gauss's theorem: electric flux over any closed surface is 1 / εo times the total charge enclosed by that surface
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Description
Learn about Coulomb's Law of Electrostatics, which describes the electrostatic force of interaction between two stationary charges. Understand the formula and its variables, including permittivity of free space.
