The most common symbol found in electrical work and diagrams is a straight, horizontal line, which represents an electrical wire, a conductor of an electrical current. Other common symbols are horizontal and vertical lines connected by filled-in dots. These represent connected electrical wires that intersect at perpendicular angles.
Electrical symbols become more complicated after the basic electrical wire and connected wire symbols. In electrical diagrams, one might find what looks like half of a vertical dumbbell pointing downward. The name of this symbols is Earth ground, and it is used a reference for zero potential and protection from electrical shock.
A resistor is represented by a zig-zagged horizontal line with two open circles on each end. It means that a resistor is present and is reducing the current flow of electricity. A resistor can also be represented by a rectangle with two horizontal lines on each end.
Another symbol is a circle containing a plus sign and minus sign with two horizontal lines on either side. It means that the item present generates constant electrical voltage. The same symbol with a right-facing arrow inside the circle represents an item that generates a constant current.
The symbol for a wattmeter is a circle with a W inside and two horizontal lines on either side. A wattmeter measures electric power.