The Electric Field

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Physics Electromagnetism The Electric Field

	A Point Charge in an Electric Field:
	When a point charge of magnitude q is placed in an electric field E, the electric force exerted on the charge is qE. If this is the only force exerted on the particle, it must be the net force and so must cause the particle to accelerate. In this case, Newton’s second law applied to the particle gives: The acceleration of the particle is thus given by, If E is uniform then the acceleration is constant. If the point charge is positive then the acceleration of the particle is in the direction of the electric field. And if the point charge is negative then the acceleration of the particle (point charge) is in the opposite direction of the electric field. A Dipole in an Electric Field: An electric dipole is defined as a positive charge Q and a negative charge –Q separated by some distance. When the dipole is inside an electric field then the dipole moment is given as: In general, the dipole moment is a vector which is directed from the negative charge towards the positive charge. A Dipole in an Electric Field: Now the torque of the dipole is given by, Here, the electric field E is given as: where y is the distance of the point at which electric field is measured from the centre of the line joining both the poles of the dipole.