Electric Circuit Elements & Definitions

Resistor
Resistor is a component used to control the magnitude of the current that flows in an electronic or electric circuit.
The magnitude of the current that flows depends on several factors, including a property of the component called its resistance.
The greater the resistance, the smaller the current. Resistance is very small in the wires joining components, but is significant in the components themselves. Resistors may be made from carbon, metal oxide, or a coil of wire. Carbon resistors are cheap but difficult to make with precisely specified resistance. Wire resistors are useful for high power, since they dissipate heat more readily than other types.

Resistors in Series and Parallel
Electric circuits with only a single path for electricity to flow along are called series circuits. Electric circuits with multiple pathways for electricity to flow along are called parallel circuits. A circuit’s total resistance to the flow of electricity is calculated differently for series circuits than it is for parallel circuits

Inductors
The inductance is the property of element by which it opposes the change in flux or current.
Inductors consist of a conducting wire wound into the form of a coil. When a current passes through the coil, a magnetic field is set up around it that tends to oppose rapid changes in current intensity. Like a capacitor, an inductor can be used to distinguish between rapidly and slowly changing voltages.
The opposition is offered by way of an induced emf opposing the current flow. Hence in an element with inductance property the current cannot change instantaneously, i.e change in current will be decayed. The unit of inductance is Henry and is denoted by H.
The inductance of a coil is defined as the ratio of flux linkages and current through the coil.

Capacitor
Capacitor is a electronic device used for storing an electrical charge, sometimes called a condenser.

In its simplest form a capacitor consists of two metal plates separated by a non-conducting layer called the dielectric. The dielectric may be air, plastic, waxed paper, or another substance such as the mineral mica. When one plate of a capacitor is charged using a battery or other source of direct current, the other plate becomes charged with the opposite sign; that is, positive if the original charge is negative, and negative if the original charge is positive.
The electrical size of a capacitor is its capacitance, that is the amount of electric charge it can hold per unit potential difference across its plates



C = Q/V


This illustration shows capacitance stored by two and more capacitors. The idea of connecting capacitors together in series or parallel is so that both the capacitance and voltage can be adjusted. As charging up a capacitor can lead to excessive temperature rises, and thus damage, it is desirable to have as large a voltage rating as possible so that the maximum amount of energy can be stored.





Impedance
The ratio of voltage and current (or) the total opposition offered to flow of current.

The unit of impedance is Ohms. Real part of impedance is resistance and the imaginary part is reactance. There two types of reactance: inductive reactance and capacitive reactance. Impedance is denoted by Z.
Impedance, Z = R+jX

Admittance
The admittance is the reverse of impedance and so the admittance is defined as the ratio of current and voltage.
The uit of admittance is Mho or siemens. The real part of admittance is conductance and imaginary part is susceptance.
Admittance, Y = G+jB

Current
Its is the characteristic property of the elementary particles of the matter. The elementary particles are electrons, protons and neutrons. There are basically two types of charges in nature: positive charge and negative charge. The charge of proton is called positive charge and the charge of electron is called negative charge. Normally a particle is neutral because it will have equal number of electrons and protons. A particle is called charged, if some electrons either added or removed from it.

Voltage
In electrical terminology the potential difference is called voltage. Every charge will have a potential energy. The difference in potential energy between the charges is called potential difference.
Voltage = energy/ charge

Power
The rate of performing work or transferring energy.
Work is equal to the force applied to move an object multiplied by the distance the object travels in the direction of the force. Power measures how quickly the work is done.
Power is the rate at which work is done.
Power is always expressed in units of energy divided by units of time. A traditional unit of power is the horsepower, which is equal to the amount of power required to lift 550 pounds at a rate of 1 foot per second. The SI unit of power is the watt, which equals the power needed to do 1 joule of work per second. There are about 746 watts in 1 horsepower.

Power = W/t .

Energy
Capacity of a physical system to perform work
Capacity to do work is call energy
Energy= power x time
Units are ……… W-s 0r J

Energy exists in various forms, including mechanical, thermal, chemical, electrical, radiant, and atomic. All forms of energy are interconvertible by appropriate processes. In the process of transformation either kinetic or potential energy may be lost or gained, but the sum total of the two always remains the same
Energy associated with motion is known as kinetic energy, and energy related to position is called potential energy.

Proton

Nuclear particle having a positive charge identical in magnitude to the negative charge of an electron and, together with the neutron, a constituent of all atomic nuclei. The proton is also called a nucleon, as is the neutron. A single proton forms the nucleus of the hydrogen atom. The mass of a proton is 1.6726 × 10-27 kg