## BIG IDEAS
Electric forces are long-range forces; no contact is required for one charged particle to exert a force on another. However, if there isn’t contact then do these interactions happen instantly?
**Electric Field Strength**
Electric field strength is a ratio of force to charge, the SI units of E are newtons per coulomb (N/C).
Field strength equation points out that the electric field at a given point depends only on the charge, _q_, and on the distance, _r_.
CONDUCTORS IN ELECTROSTATIC EQUILIBRIUM
No net motion of charge is occurring within a conductor then the conductor is said to be in _electrostatic equilibrium_.
- The electric field is zero everywhere inside the conductor.
- Any excess charge on an isolated conductor resides entirely on the conductor’s outer surface.
- The electric field just outside a charged conductor is perpendicular to the conductor’s surface.
On an irregularly shaped conductor, charge tends to accumulate where the radius of curvature of the surface is smallest, that is at sharp points.
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