BASIC ELECTRONIC COMPONENT KNOWLEDGE

WHAT IS RESISTORS?

A resistor is a component of an circuit that resists the flow of electrical current. It has two terminals across which electricity must pass, and it is designed to drop the voltage of the current as it flows from one terminal to the other. Resistors are primarily used to create and maintain known safe currents within electrical components.

resistor color code

What is capacitor

Capacitor is an electronic component that stores electric charge. The capacitor is made of 2 close conductors (usually plates) that are separated by a dielectric material. The plates accumulate electric charge when connected to power source. One plate accumulates positive charge and the other plate accumulates negative charge.

The capacitance is the amount of electric charge that is stored in the capacitor at voltage of 1 Volt.

The capacitance is measured in units of Farad (F).

The capacitor disconnects current in direct current (DC) circuits and short circuit in alternating current (AC) circuits.

Capacitor symbols

Capacitor
Polarized capacitor
Variable capacitor

Capacitor types

Variable capacitor	Variable capacitor has changeable capacitance
Electrolytic capacitor	Electrolytic capacitors are used when high capacitance is needed. Most of the electrolytic capacitors are polarized
Spherical capacitor	Spherical capacitor has a sphere shape
Power capacitor	Power capacitors are used in high voltage power systems.
Ceramic capacitor	Ceramic capacitor has ceramic dielectric material. Has high voltage functionality.
Tantalum capacitor	Tantalum oxide dielectric material. Has high capacitance
Mica capacitor	High accuracy capacitors
Paper capacitor	Paper dielectric material

capacitor colour code

what is diode?

In simple language, a diode is like one-way valve which allows electric current to flow in one direction but generally does not allow it to flow in the opposite direction. The direction of the electric current in the diode may be reversed. However, even if it is, the flow will still be one directional.

A diode can convert electric current from AC to DC or from Alternating Current to Direct Current. This is called rectification, and rectifier diodes are most commonly used in low current power supplies. A switching diode is most often used to turn a circuit on or off, and band switching diodes are used for switching high frequency band signals. A Zener diode is known as a constant voltage diode, due to the fact that even if power supply voltage varies, the Zener voltage remains at a constant level. A Schottky barrier diode, when used for high speed switching rather than basic rectification, is used for things like UHF and other high frequency signals.

A diode can be used for various purposes including the production of different signals such as an analog signal, frequencies such as microwave frequencies, or light. Those that produce light are known as Light Emitting Diodes or LED. This type of diode will produce light when current flows through it. LED are used for things like lighted elements in computer systems, clocks, displays on microwaves and electronics, solar lighting, and even some of the more modern designs in Christmas lights.

Picture of diodes

What Is A Transistor

A Transistor is an semiconductor which is a fundamental component in almost all electronic devices. Transistors are often said to be the most significant invention of the 20th Century. Transistors have many uses including switching, voltage/current regulation, and amplification - all of which are useful in renewable energyapplications. 

A transistor controls a large electrical output signal with changes to a small input signal. This is analogous to the small amount of effort required to open a tap (faucet) to release a large flow of water. Since a large amount of current can be controlled by a small amount of current, a transistor acts as an amplifier.

A transistor acts as a switch which can open and close many times per second.

Bipolar Junction Transistors

The most common type of transistor is a bipolar junction transistor. This is made up of three layers of a semi-conductor material in a sandwich. In one configuration the outer two layers have extra electrons, and the middle layer has electrons missing (holes). In the other configuration the two outer layers have the holes and the middle layer has the extra electrons.

Layers with extra electrons are called N-Type, those with electrons missing called P-Type. Therefore the bipolar junction transistors are more commonly known as PNP transistors and NPN transistors respectively.

Bipolar junction transistors are typically made of silicon and so they are very cheap to produce and purchase.

How do Transistors Work

A bipolar junction transistor has three terminals - Base, Collector, and Emitter corresponding to the three semi-conductor layers of the transistor. The weak input current is applied to the inner (base) layer. When there is a small change in the current or voltage at the inner semiconductor layer (base), a rapid and far larger change in current takes place throughout the whole transistor.

Pictured above is a schematic diagram of the more common NPN transistor. Below is an illustration of the same transistor using water rather than electricity to illustrate the way it functions:

The illustration shows pipework with three openings B (Base), C (Collector), and E(Emitter). The reservoir of water at C is the supply voltage which is prevented from getting though to E by a plunger. If water is poured into B, it pushes up the plunger letting lots of water flow from C to E. If even more water is poured into B, the plunger moves higher, and the flow of water from C to E increases.

Therefore, a small input current of electricity to the Base leads to a large flow of electricity from the Collector to the Emitter.

Transistor Gain

Looking at the water analogy again, if it takes 1 litre of water per minute poured into B to control 100 litres of water per minute flowing from C to E, then the Gain (or amplification factor) is 100. A real transistor with a gain of 100 can control 100mA of current from C to E with an input current of just 1mA to the base (B).

If the output power (current x voltage) are more than 1 Watt a Power Transistor must be used. These let much more power flow through, and require a larger controlling input current.

Simple Transistor Circuit

Pictured above is a very simple circuit which demonstrates the use of transistors. When a finger is placed in the circuit where shown, a tiny current of around 0.1mA flows (assuming a finger resistance of 50,000 Ohms). This is nowhere near enough to light the LED which needs at least 10mA. However the tiny current is applied to theBase of the transistor where it is boosted by a factor (gain) of around 100 times and the LED lights!

what is inductor?

An inductor is a passive electronic component dependent on frequency used to store electric energy in the form of a magnetic field. An inductor has the symbol

An inductor is about as simple as an electronic component can get -- it is simply a coil of wire. It turns out, however, that a coil of wire can do some very interesting things because of the magnetic properties of a coil.

Inductor Basics

In a circuit diagram, an inductor is shown like this:

To understand how an inductor can work in a circuit, this figure is helpful:

What you see here is a battery, a light bulb, a coil of wire around a piece of iron (yellow) and a switch. The coil of wire is an inductor. If you have read How Electromagnets Work, you might recognize that the inductor is an electromagnet.

If you were to take the inductor out of this circuit, what you would have is a normal flashlight. You close the switch and the bulb lights up. With the inductor in the circuit as shown, the behavior is completely different.

The light bulb is a resistor (the resistance creates heat to make the filament in the bulb glow -- seeHow Light Bulbs Work for details). The wire in the coil has much lower resistance (it's just wire), so what you would expect when you turn on the switch is for the bulb to glow very dimly. Most of the current should follow the low-resistance path through the loop. What happens instead is that when you close the switch, the bulb burns brightly and then gets dimmer. When you open the switch, the bulb burns very brightly and then quickly goes out.

The reason for this strange behavior is the inductor. When current first starts flowing in the coil, the coil wants to build up a magnetic field. While the field is building, the coil inhibits the flow of current. Once the field is built, current can flow normally through the wire. When the switch gets opened, the magnetic field around the coil keeps current flowing in the coil until the field collapses. This current keeps the bulb lit for a period of time even though the switch is open. In other words, an inductor can store energy in its magnetic field, and an inductor tends to resist any change in the amount of current flowing through it.

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