# Function of Capacitor

Description

A capacitor contains electrodes, which consist of two metal plates or metal films that face each other. An insulator (or a dielectric substance), which can be made of various materials, is placed between the electrodes. (In the diagram, air acts as an insulator.)
When voltage is applied to both electrodes by connecting the positive and negative terminals of a battery, the facing electrodes will become positively and negatively charged.
The electric charges will remain even after the power source has been disconnected, as the capacitor has a charging effect. When the electrodes of a charged capacitor are shorted, there will be a momentary flow of current, and the stored charge will become neutralized and disappear. Thus, the capacitor is discharged. Read more Function of Capacitor

# Relay and Fuse

Relay

If the electrical circuit for devices requiring a high amperage consists of a power source, a switch, and a light bulb that are directly connected, the switch and the wiring harness must be of a high capacity that can withstand the high amperage. However, through the use of a low-amperage current, a switch can turn a relay ON and OFF, which in turn, can apply the high amperage that flows to turn the light bulb ON and OFF.

The diagram on the left describes the mechanism of a relay. When the switch closes, the current flows between points 1 and 2, thus magnetizing the coil. The magnetic force of the coil attracts the moving contact between points 3 and 4. As a result, points 3 and 4 close and allow the current to flow to the light bulb. Thus, through the use of a relay, the switch and the wiring harness to the switch can be of a low capacity.

# Basic of Electrical Circuit

Voltage and current

The speed of the waterwheel changes by changing the water volume in the tank. This means that the speed of the water flowing to the waterwheel changes with the change in the water pressure in the tank.
When this phenomenon of water is substituted with electricity, the water volume (water pressure) is the voltage, and the water flow is the electrical current.

Current and resistance
The force of the water flow changes with the height of the gate that is located between the tank and the waterwheel. As a result, the speed of the waterwheel changes.
This gate is equivalent to the resistance in an electrical circuit. Read more Basic of Electrical Circuit

# Fundamentals of Automotive electricity

Electrical Circuit

Electrical devices are used in numerous areas of an automobile, and provide various functions.
As electricity passes through a resistor, it affects the resistor and can provide a number of functions.
Electrical devices utilize those functions according to purpose by converting electricity into work.
Functions of electricity
1. Heat-generation function
Heat is generated as electricity passes through a resistor, such as a cigarette lighter, fuse.
2. Light-emitting function
Light is emitted as electricity passes through a resistor, such as a light bulb. Read more Fundamentals of Automotive electricity