Resistors

In a correctly protected circuit, the fuse is placed ‘Inline’ between the power source in this case the battery and the lamp. If the lamp goes ‘short circuit’, a massive current will begin to flow and the fuse will fail causing an open circuit. The battery and wiring are protected from over current damage.

Below is the fuse symbol as shown on the circuit diagrams. The number above the fuse symbol is the fuse number; allocated to this fuse. The number below the fuse symbol is the rating.

Resistors

A resistor is an electronic component that by way of its construction reduces the current flowing through it. A resistors unit of measure is the Ohm.

The diagrams below show a resistor and a variable resistor.

Variable Resistors

A variable resistor works in the same manner as a normal resistor but the resistance values can fluctuate. The construction of a variable resistor depends upon its use and environment.

One example is for the fuel tank level sensor. The tank full level is 10 ohms and the tank empty level is 204 ohms, the resistance will vary between 10 and 204 ohms depending on how much fuel is in the tank.

Lamps

Below is the symbol for a light bulb, shown below the symbol is the power of the bulb in watts.

Switches

There are numerous of types of switch, several of examples are shown below.

Normally Open Switch

2 Position Switch

3 Position Switch

Motors and Pumps

The same symbol is used for a pump or a motor, the description differentiates between them.

Pump