Physics Definition 2

The sum of the magnitudes of the currents directed into a junction equals the sum of the magnitudes of the currents directed out of a junction.

The current through a conductor between two points is directly proportional to the potential difference across the two points. V=IR

The electric potential V at given point is the electric potential energy EPE of a small test charge q_o situated at that point, divided by the charge itself V=EPE/q_o

During any process, the net electric charge of an isolated system remains constant

The electric force, F, per unit charge that is operating on a small test charge q_o (+) at that point.

• Electric charges create an electric field
• Electric Field lines are used to indicate the direction and strength of that field.

• - Lines go towards negative charges and away from positive charges
• - Lines radiate into three-dimensional space
• - Lines start at a positive charge and finish at a negative one, i.e. they do not terminate mid-way between charges
• - Lines cannot cross each other
• - When field lines are parallel to each other (i.e. equidistant from each other), this indicates that electric field strength is uniform
• - When electric field lines are close together, this indicates the region where the field strength is greatest

Two point charges with the same magnitude but opposite sign, separated by distance, d.

• The amount of work W=q_o V must be done to move a charge q_o through a potential difference, V, 1.6x10^-19 C is the charge on the electron, and therefore, to move it through a potential difference of 1V, the amount of work that must be done is W=1.6x10^-19 C x 1V = 1.6x10^-19 J
•              1eV = 1.6x10^-19 J

• Spherical surfaces which have the same electric potential at every point.
• No work is done be the electric force when a test charge moves along any route on an equipotential surface.

• W_ABC=0
• Work IS done when a test charge moves BETWEEN equipotential surfaces W_AD≠0