Dasar-dasar listrik

Sebetulnya kita sudah mengenal listrik,karena sehari-hari kita menggunakannya.Kalau kita menekan tombol saklar lampu, energi listrik akan ke lampu dan menghasilkan cahaya. Jika kita menggunakan blender, motor akan berputar. Lampu senter menggunakan batu batere sebagai sumber energi dan ketika batere soak, batere tidak akan menghasilkan listrik yang cukup untuk menyalakan lampu senter
In fact most of us have a slightly more advanced knowledge of electricity than we may realize. You have probably noticed that most electrical devices have two wires feeding power to them, or that light bulbs have a brilliant glow and they are very hot during operation. If you leave the car�s lights on overnight you know that the battery will be dead the next morning. You may also be aware that a car operates on 12 volts DC and the outlets in the house supply 120 volts AC.
The Electric Circuit
In order to better utilize the information presented in this lesson, it is necessary to have a basic understanding of electricity and how it can be applied to work with, or provide control for, mechanical devices.
To better understand electricity, let�s first consider the basic electric circuit. All electrical circuits have two things in common, they have a power source and something that is using that power, generally referred to as the load. In Figure above the power source is a battery and the load is a light bulb. The battery supplies energy to the light bulb and the bulb�s filament glows. In this arrangement, the stored energy of the battery is transformed into something useful, light. Electrons flow from the negative terminal (�) of the battery through the
light bulb filament and back to the positive terminal (+). To make the basic electrical a little more friendly, a switch is applied to the circuit. The switch is much like a valve for electrons. When the switch is open, as shown in Figure above,
the flow of electrons is interrupted and the lamp is off. This mode is usually referred to as an open circuit. To turn the lamp on, the switch is closed and the electrons can flow again, as shown in Figure below. This mode is generally referred to as a closed circuit. The switch provides ready convenience in operating the circuit.