If there is a strong enough electric field, sparks form in the air where the electricity jumps from one object to another. In this chapter, we discuss electrical energy and electric potential.
- The electric field between two parallel-plate conductors is considered uniform far away from the plate edges if the size of the plates is large compared to their separation distance.
- The potential energy of a charge at a point between two parallel-plate conductors is , a reference point must be given such as at .
- A point charge has electric potential energy and electric potential at point . Thus,
- The word voltage is used when we mean potential difference.
- It is common to write , where is understood to mean the voltage (or potential difference) between the plates of a parallel-plate conductor and is the distance between the plates.
- The work done by the electric field in moving a charge between two parallel plate conductors is . The work done by an external force is .
- Voltage can be thought of as the work per unit charge ; that is, how much work is required per unit charge to move a charged particle in an electric field.
- Capacitance of an air-gap capacitor is given by where is the area of the capacitor and is the separation distance between the plates.
- The charge on a capacitor is directly proportional to the voltage of the capacitor .
- A dielectric material placed between the plates increases the capacitance of the capacitor. The capacitance of a capacitor with a dielectric is expressed as , where is the dielectric constant.
- The energy stored in a capacitor can be expressed as
Where is the charge on the capacitor and is the voltage of the capacitor.