Electric field
To help visualize how a charge, or a
collection of charges, influences the region around it, the concept of an
electric field is used. The electric field E is analogous to g, which we
called the acceleration due to gravity but which is really the
gravitational field. Everything we learned about gravity, and how masses
respond to gravitational forces, can help us understand how electric
charges respond to electric forces.
The electric field a distance r away from a
point charge Q is given by:
Electric field from a point charge : E = k
Q / r2
The electric field from a positive charge
points away from the charge; the electric field from a negative charge
points toward the charge. Like the electric force, the electric field E is
a vector. If the electric field at a particular point is known, the force
a charge q experiences when it is placed at that point is given by :
F = qE
If q is positive, the force is in the same
direction as the field; if q is negative, the force is in the opposite
direction as the field. |