Intensive property of matter particle due to which they experience force of attraction or repulsion. S.I. unit of electric charge is Coulomb (C), which is equivalent to the charge contained in nearly 6 x 1018 electrons. Properties Of Charge: (i) Additive Nature (ii) Conservation of Charge (iii) Quantisation of Charge

Electric current is a flow of electric charge through a medium. This charge is typically carried by moving in a conductor such as wire. It can also be carried by ions in an electrolyte, or by both ions and electrons in a plasma.The SI unit for measuring the rate of flow of electric charge is the ampere, which is charge flowing through some surface at the rate of one coulomb per second. Electric current is measured using an ammeter.

An electric circuit is a closed path for flow of electricity An through which electricity can be converted into different forms. An electric circuit basically contains a source of electricity, a load resistance, a switch or a key for making the circuit on or off at ones convenience (which makes or breaks the circuit correspondingly). The diagrammatic representation of an electric circuit is called the circuit diagram. Each electric component in a circuit has a unique symbol through which it is represented in a circuit diagram. If a circuit is switched off, it is called an open circuit and if the circuit is switched on it is called a closed circuit. When two or more resistors are connected such a way that the terminus of one resistance is connected to the starting end of the other, such a combination of resistance is called the series connection and the circuit is called series circuit.

On the other hand, if the starting ends of two resistors are joined to a point and the terminal ends of the two are combined and given connection to a source of electricity, such a combination is called parallel connection and the circuit is called parallel circuit. The potential difference or voltage drop across a resistance is the cause of electric current through it. For a number of resistors connected in series, the electric current through them remains the same and the potential drop across each of them varies as their resistance. The net resistance or equivalent resistance of a number of resistors connected in series is the sum of the individual resistance. The reciprocal of the net resistance or equivalent resistance of a number of resistors connected in parallel is the sum of the reciprocals of the individual resistances

We define the electric potential difference between two points in an electric circuit carrying some current as the work done to move a unit charge from one point to other-Potential difference (V) between two points = Work done (W) / Charge (Q) V = W/Q The S.I. unit of electric potential difference is Volt (V) . One volt is the potential difference between two points in a circuit carrying conductor when 1 Joule of work is done to move a charge of 1 coulomb from one point to other. Therefore, 1 volt = 1 joule/1coulomb 1 V = 1 JC

A circuit diagram (also known as an electrical diagram, elementary diagram, or electronic schematic) is a simplified conventional graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components of the circuit as simplified standard symbols; both types show the connections between the devices, including power and signal connections. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points, and inversely proportional to the resistance between them.[1]The mathematical equation that describes this relationship is

where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[3]

The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire. He presented a slightly more complex equation than the one above (see History section below) to explain his experimental results. The above equation is the modern form of Ohm's law.

Resistance is the property of a component which restricts the flow of electric current. Energy is used up as the voltage across the component drives the current through it and this energy appears as heat in the component. Resistance is measured in ohms, the symbol for ohm is an omega . 1 is quite small for electronics so resistances are often given in k and M . 1 k = 1000 1 M = 1000000 . Resistors used in electronics can have resistances as low as 0.1 or as high as 10 M .

If the resistance is constant over a considerable range of voltage, then Ohm's law, I = V/R, can be used to predict the behavior of the material. Although the definition above involves DC current and voltage, the same definition holds for the AC aWhether or not a material obeys Ohm's law, its resistance can be described in terms of its bulk resistivity. The resistivity, and thus the resistance, is temperature dependent. Over sizable ranges of temperature, this temperature dependence can be predicted from a temperature coefficient of resistance pplication of resistors.

The electrical resistance of a wire would be expected to be greater for a longer wire, less for a wire of larger cross sectional area, and would be expected to depend upon the material out of which the wire is made. Experimentally, the dependence upon these properties is a straightforward one for a wide range of conditions, and the resistance of a wire can be expressed as

The factor in the resistance which takes into account the nature of the material is the resistivity . Although it is temperature dependent, it can be used at a given temperature to calculate the resistance of a wire of given geometry. The inverse of resistivity is called conductivity. There are contexts where the use of conductivity is more convenient.Electrical conductivity = = 1/

resistorsThe combination rules for any number of resistors in series or parallel can be derived with the use of Ohm's Law, the voltage law, and the current law. Resistors connected in Series:When resistors are connected in series their combined resistance is equal to the individual resistances added together. For example if resistors R1 and R2 are connected in series their combined resistance, R, is given by: Combined resistance in series: R = R1 + R2 This can be extended for more resistors: R=R1+R2+R3+R4+...

Resistors connected in Parallel:When resistors are connected in parallel their combined resistance is less than any of the individual resistances. There is a special equation for the combined resistance of two resistors R1 and R2: Combined resistance of two resistors in parallel: R =R1 R2R1 + R2For more than two resistors connected in parallel a more difficult equation must be used.

This adds up the reciprocal ("one over") of each resistance to give the reciprocal of the combined resistance. The simpler equation for two resistors in parallel is much easier to use!

Heating effect of electricity is one of the widely used effects in the world. When electric current is passed through a conductor, it generates heat due to the resistance it offers to the current flow. The work done in overcoming the resistance is generated as heat. This is studied by James Prescott Joule and he enunciated various factors that affect the heat generated. The heat produced by a heating element is directly proportional to the square of the electric current (I) passing through the conductor, directly proportional to the resistance (R) of the conductor, time (t) for which current passes through the conductor. It is given by the expression H = I2Rt and is well known as Joules Law.

Applications of the heating effect of electric current include appliances like electric immersion water heater, electric iron box, etc. All of these have a heating element in it. Heating elements are generally made of specific alloys like, nichrome, manganin, constantan etc. A good heating element has high resistivity and high melting point. An electric fuse is an example for the application of heating effect of electric current. The rating of 3 A of an electric fuse implies the maximum current it can sustain is three ampere.

Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.When electric current flows in a circuit, it can transfer energy to do mechanical or thermodynamic work. Devices convert electrical energy into many useful forms, such as heat (electric heaters), light (light bulbs), motion (electric motors), sound (loudspeaker), information technological processes (computers), or even chemical changes. Electricity can be produced mechanically by generation, or chemically, or by direct conversion from light in photovoltaic cells, also it can be stored chemically in batteries.

Electric power, like mechanical power, is represented by the letter P in electrical equations. The term wattage is used colloquially to mean "electric power in watts."In direct current resistive circuits, electrical power is calculated using Joule's law:

where P is the electric power, V the potential difference, and I the electric current.In the case of resistive (Ohmic, or linear) loads, Joule's law can be combined with Ohm's law (I = V/R) to produce alternative expressions for the dissipated power: