Current always moves from high voltage to low voltage.
Therefore, if it passes through a resistor, one end of the
resistor (into which the current flows) must be at a higher
voltage than the other end (out of which the current flows).
The difference in voltage between the two ends of a resistor
is called the voltage drop across the resistor.
It is equal to
voltage drop = (current) * (resistance)
Batteries (and power supplies) raise the voltage in a circuit.
The long end of a battery symbol is at a higher voltage than
the short end.
The battery tries to push current away from its positive terminal
(long end of the symbol).
Ohm's Laws describe the behavior of current flowing through
a circuit:
The magnitude of the current flowing into a junction must
equal the magnitude of the current flowing out of that junction.
The sum of voltage rises and drops around any closed loop in
a circuit is equal to zero.
Using Ohm's Law, one can solve for the current flowing through
simple or complex circuits.
