# Kirchoff's Rules

• 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:
1. The magnitude of the current flowing into a junction must equal the magnitude of the current flowing out of that junction.
2. 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.

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