The Physics
Hypertextbook
Opus in profectus

# Electric Field

## Discussion

### introduction

Some text and some diagrams. The electric field as a vector field.

And more diagrams. The electric field as field lines.

And maybe some mathematics. In classical field theory, the strength of the field at a point is the normalized value of the field. In other words…

 field = force quantity

For electricity, this becomes…

 E = FE q

There is no special name for its unit, nor does it reduce to anything simpler.

 ⎡⎢⎣ N = kg m/s2 = kg m ⎤⎥⎦ C A s A s3

We will see later that this is equivalent to…

 ⎡⎢⎣ N = V ⎤⎥⎦ C m

For point charges…

 E = 1 q r̂ or E = k q r̂ 4πε0 r2 r2

For multiple point charges…

 E = 1 ∑ dq r̂ or E = k ∑ dq r̂ 4πε0 r2 r2

For continuous charge distributions…

 E = 1 ⌠⌡ dq r̂ or E = k ⌠⌡ dq r̂ 4πε0 r2 r2
Electric field strength (smallest to largest)
E (V/m) device, event, phenomenon, process
5.0 × 10−7 shark, threshold of sensitivity
120 earth's surface (sea level)
3 × 106 dielectric breakdown of air