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### Electric Fields & Potential

• An electric field (E) is a location that exerts a force on a charge based on the amount of the charge. Given a point charge q1 and a distance r, we can figure out this value.

E

= k q1

r2
=  → Fe

q2
.
The electric field always points in the direction a positive charge would move.
• The strength of an electric field is measured in newtons per coulomb ([N/C]).
• Electric field lines are a way to visualize electric fields at many points. They always point in the direction a positive charge would move.
• A Faraday cage is a fully enclosing conductor. Electric fields outside the cage will have no effect inside of it, and vice-versa.
• Electric potential (V) is connected to the amount of work involved in moving a charge and how much charge we are moving. Each location has a potential V tied to it. To figure out how much work is involved in moving from one location to another, we need to look at the potential difference:
 ∆V = W q .
• Electric potential is measured in volts (V): joules per coulomb ([J/C]). A difference in electric potentials is called a voltage.
• Like setting a base height when we worked with gravitational potential energy, we need to set an arbitrary base electric potential. We often use the ground (the literal body of the Earth) for this, setting it as 0V.
• An electron-volt is a very small unit of energy. It is how much energy is involved in moving a single elementary charge (e) across a voltage of 1V:
 1 eV = 1.602 ·10−19J.
• An equipotential surface is something where it takes no work to move charge around (equal electric potential means no voltage means no work).

## Electric Fields & Potential

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.