Electric Circuits Book

[Colette]

We know various components are needed to build an electrical circuit. To understand the electrical circuit and the flow of current, one must understand the electrical symbols of circuit components. In this article, let us discuss in brief about electric circuit and its components.

An electrical circuit is complete only when there is at least one closed loop from the positive to the negative end. This is the simplest form of an electric circuit. The circuit found inside a television is more complicated and has different components.

You might have seen these danger signs on electric poles, transformers, and sometimes even on some electrical equipment at home. It is to warn you about the dangers of electricity, and electricity, if not handled properly, could be lethal and can even cause death. Electric wires sockets and live wire should be adequately insulated and kept away from the reach of children, the voltage in a small battery does not exceed more than 12 volts, but the voltage in a transformer may reach up to 11000 volts.

We have come to a conclusion that electric current flows only when there is a complete uninterrupted connection from a battery through different components back to the battery. Any interruption will stop the flow of current

Electric batteries should also be handled carefully; never connect two terminals of the battery without a bulb or a load because the chemicals inside the battery react so quickly that they generate an immense amount of energy, which can even cause them to burst.

Every component and product of the electric circuit contains a symbol. The symbols represent parts of the circuit in a circuit diagram. Beneath are the basic set of symbols that are present in a circuit diagram.

A circuit is a closed path that consists of circuit components in which electrons from a voltage or current source can flow. If the circuit consists of electric components like a resistor, a capacitor, an inductor etc. then it will be called an Electrical circuit and if the circuit consists of any of the electronic circuit components like a diode, a Transistor etc. then it will be called an Electronic circuit. So, the electronic circuits may consist both of the electrical and electronic circuit components, but an electrical circuit will have only the electrical components.

The point where electrons enter an electrical circuit is called the "source" of electrons. The point where the electrons leave an electrical circuit is called the "return" or "earth ground". The exit point is called the "return" because electrons always end up at the source when they complete the path of an electrical circuit.

The part of an electrical circuit that is between the electrons' starting point and the point where they return to the source is called an electrical circuit's "load". The load of an electrical circuit may be as simple as those that power home appliances like refrigerators, televisions, or lamps or more complicated, such as the load on the output of a hydroelectric power generating station.

Circuits use two forms of electrical power: alternating current (AC) and direct current (DC). AC often powers large appliances and motors and is generated by power stations. DC powers battery-operated vehicles and other machines and electronics. Converters can change AC to DC and vice versa. High-voltage direct current transmission uses big converters.

Electronic circuits usually use direct current sources. The load of an electronic circuit may be as simple as a few resistors, capacitors, and a lamp, all connected together to create the flash in a camera. Or an electronic circuit can be complicated, connecting thousands of resistors, capacitors, and transistors. It may be an integrated circuit such as the microprocessor in a computer.

A circuit or wiring diagram is a visual display of an electrical circuit. Electrical and electronic circuits can be complicated. Making a drawing of the connections to all the component parts in the circuit's load makes it easier to understand how circuit components are connected. Drawings for electronic circuits are called "circuit diagrams". Drawings for electrical circuits are called "wiring diagrams". Like other diagrams, these diagrams are usually drawn by draftsmen, and then printed. Diagrams may also be created digitally using specialised software.

A schematic is a diagram of an electrical circuit. Schematics are graphical representations of the essential connections in a circuit, but they are not lifelike depictions of a circuit. Schematics use symbols to represent components in the circuit. Conventions are used in a schematic to represent the way electricity flows. The common convention we use is from the positive to the negative terminal. The realistic way electricity flows is from the negative to the positive terminal.

Circuit diagrams use special symbols. The symbols on the drawings show how components like resistors, capacitors, insulators, motors, outlet boxes, lights, switches, and other electrical and electronic components are connected together. The diagrams are a big help when workers try to find out why a circuit does not work correctly.

The current flowing in an electrical or electronic circuit can suddenly increase when a component part fails. This can cause serious damage to other components in the circuit, or create a fire hazard. To protect against this, a fuse or a device called a "circuit breaker" can be wired into a circuit. The circuit breaker will open, or "break", the circuit when the current in that circuit becomes too high, or the fuse will "blow". This gives protection.

The standard return for electrical and electronic circuits is the earth ground. When an electrical or electronic device fails, it may open the return circuit to the earth ground. The user of the device could become a part of the device's electrical circuit by providing a return path for the electrons through the user's body instead of the circuit's earth ground. When our body becomes part of an electrical circuit, the user can be seriously shocked, or even killed by electrocution.

To prevent the danger of electrical shock and the possibility of electrocution, ground fault interrupts devices detect open circuits to earth ground in attached electrical or electronic devices. When an open circuit to earth ground is detected, the G.F.I. device immediately opens the voltage source to the device. G.F.I. devices are similar to circuit breakers but are designed to protect humans rather than circuit components.

Short circuits are circuits that get back to the power source unused or with the same power as put out. Using these usually blow a fuse but sometimes they don't. Doing this with a battery can cause electrical fires.

An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit. For a circuit to be referred to as electronic, rather than electrical, generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another.[1]

Circuits can be constructed of discrete components connected by individual pieces of wire, but today it is much more common to create interconnections by photolithographic techniques on a laminated substrate (a printed circuit board or PCB) and solder the components to these interconnections to create a finished circuit. In an integrated circuit or IC, the components and interconnections are formed on the same substrate, typically a semiconductor such as doped silicon or (less commonly) gallium arsenide.[2]

The basic components of analog circuits are wires, resistors, capacitors, inductors, diodes, and transistors. Analog circuits are very commonly represented in schematic diagrams, in which wires are shown as lines, and each component has a unique symbol. Analog circuit analysis employs Kirchhoff's circuit laws: all the currents at a node (a place where wires meet), and the voltage around a closed loop of wires is 0. Wires are usually treated as ideal zero-voltage interconnections; any resistance or reactance is captured by explicitly adding a parasitic element, such as a discrete resistor or inductor. Active components such as transistors are often treated as controlled current or voltage sources: for example, a field-effect transistor can be modeled as a current source from the source to the drain, with the current controlled by the gate-source voltage.

When the circuit size is comparable to a wavelength of the relevant signal frequency, a more sophisticated approach must be used, the distributed-element model. Wires are treated as transmission lines, with nominally constant characteristic impedance, and the impedances at the start and end determine transmitted and reflected waves on the line. Circuits designed according to this approach are distributed-element circuits. Such considerations typically become important for circuit boards at frequencies above a GHz; integrated circuits are smaller and can be treated as lumped elements for frequencies less than 10GHz or so.

In digital electronic circuits, electric signals take on discrete values, to represent logical and numeric values.[4] These values represent the information that is being processed. In the vast majority of cases, binary encoding is used: one voltage (typically the more positive value) represents a binary '1' and another voltage (usually a value near the ground potential, 0 V) represents a binary '0'. Digital circuits make extensive use of transistors, interconnected to create logic gates that provide the functions of Boolean logic: AND, NAND, OR, NOR, XOR and combinations thereof. Transistors interconnected so as to provide positive feedback are used as latches and flip flops, circuits that have two or more metastable states, and remain in one of these states until changed by an external input. Digital circuits therefore can provide logic and memory, enabling them to perform arbitrary computational functions. (Memory based on flip-flops is known as static random-access memory (SRAM). Memory based on the storage of charge in a capacitor, dynamic random-access memory (DRAM), is also widely used.)

c80f0f1006