1. 1 CHAPTER-22 Electric Field

2. 2 Ch 22-2 Electric Field  Field: Region of space characterized by a physical property  Scalar physical property- scalar field; vector physical property- vector field  The Electric Field characteristics: Exerts force on a positive test charge  Electric field is due to a charge and surrounds it  Direction of E( given by arrow head): away from a positive charge and towards a negative charge

3. 3  Space around charge filled with lines of force or electric field lines  Direction of E-field lines or direction of the tangent to a curved field line gives the direction of E at that point.  Number of E-field lines per unit area, measured in a plane  to the lines, is proportional to the magnitude of E.  Closer lines, larger E and farther the lines, the weaker is E field  Parallel E field lines means uniform E-field Ch 22-3 Electric Field Lines

4. 4 Ch 22-4 Electric Field Due to a Point Charge  Electric Field due to a point charge  E=F/q 0 =k  q 2  /r 2  E-field due to sum of Charges: E net =  E i =E 1 +E 2 +E 3 +…. q qoqo r P

5. 5 Ch 22-4 Electric Field Due to a Point Charge  Field between three charges:  Zero Net Field location :  For opposite charges, it is on the sides of the charges and nearer to weaker charge  For similar charges, it is between the charges and nearer to weaker charge

6. 6 Ch 22-5 Electric Field Due to a Electric Dipole  Electric Field Due to a Electric Dipole  E d =2kqd/z 3= (1/2  0 ) p/z 3 where p is electric dipole moment given by: p=qd direction of p is taken from negative end to positive end of dipole

7. 7 Ch 22-8 A Point Charge in an Electric Field  The electrostatic force F on a charge q in an external field E is in the direction of E for positive charge and in opposite direction for negative charge

8. 8 Ch 22-9 A Dipole in an Electric Field  Net torque on the dipole  = p xE =pEsin   Negative torque for clockwise rotation  =- pEsin   Positive torque for counterclockwise rotation  =pEsin   Potential Energy U of a Dipole (U 90 =0)  U=-W=-   90  d  =   90 pEsin  d   U=-p Ecos  = -p.E  U min =-pE (  =0); U max =+pE(  =180);  W=-  U=-(U f -U i ) F+F+ F-F- x-axis