electric circuit

An electric circuit is a closed path for flow of electricity 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 parallel, the electric potential drop across them remains the same and the electric current through each of them varies as their resistance.
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 resistances.

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.

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