**Current:**

Electrical charge flow past a given point per unit of time.

**Direct current:**

Electrical current that flows in only one direction.

**Alternating current:**

Electrical current that oscillates forward and backwards.

**Voltage:**

The ratio of electric potential energy to electric charge at a particular spot in an electric field. It is often referred to as voltage since it is measured in volts.

**Ohm’s law:**

Basic law that describe current electricity; Voltage equals current times resistance.

**Internal resistance:**

Resistance from the processes inside a voltage source; reistance due to the battery itself.

**Series circuit:**

A circuit where the components form one continuous loop. The current is constant throughout.

**Parallel circuit:**

A circuit where each component is connected to form its own separate independent branch. The voltage is constant throughout.

**Fuse/Circuit breaker:**

A safety device designed to melt or disconnect a circuit after a predetermined amount of current is exceeded.

**Junction rule:**

A restatement of conservation of charge; the current going into a junction must equal the current going out of the junction.

**Loop rule:**

A restatement of conservation of energy; the sum of all voltages in the elements of a loop is zero.