ELECTRIC FIELD NOTES : ELECTRIC FIELD

 Electric Field:

 Electric field is a region of space around a charge or a system of charges within which other charged particles experience electrostatic forces.


Electric Field Strength or Electric Field Intensity or Electric Field: 

Electric field strength at a point in an electric field is the electrostatic force per unit positive charge acting on a vanishingly small positive test charge placed at that point.

𝑬 = 𝑭/𝒒₀




The test charge is considered to be vanishingly small  because its presence should not alter the configuration of the source charge and thus the electric field which is intended to be measured.

 Since 𝒒₀ is taken positive, the direction of electric field ( E ) is along the direction of electrostatic force ( F ). 


 Electric field is a vector quantity whose magnitude and direction are uniquely determined at every point in the field. 

SI unit of electric field is newton / coulomb ( NC⁻¹ ).


The electric field produced by a point charge q 

 The magnitude of the force exerted by the charge q on a test charge q₀ is, 




F= `\frac{1}{4 πε_{0}}` `\frac{q_{}q_{0}}{r^{2}}`

E= F/q0 =

 F= `\frac{1}{4 πε_{0}}` `\frac{q_{}}{r^{2}}`

If q is positive, E is directed away from q. On the other hand, if q is negative, then E is directed towards q. 




ELECTRIC FIELD INTENSITY DUE TO A GROUP OF CHARGES OR SUPERPOSITION PRINCIPLE : 

Electric field intensity at any point due to a group of point charges is equal to the vector sum of electric field intensities due to individual charges at the same point. 



Electric lines of force: 

The paths, along which the unit positive charge will move due to electrostatic force in the field are called electric lines of force. 

The tangent at any point on the electric lines of force gives the direction of electric field at that point.

The properties of electric lines of force are: 

  • i) Electric lines of force start from positive charge and terminate at negative charge. 
  • ii) Electric Lines of force never intersect each other ( see explanation below)
  • iii) Electric lines of force emerge or terminate at right angle to the surface of charge. 
  • iv) ..

 


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