 # Electric Circuit

An electric circuit is a path through which electric current flows. An electric circuit can also be a closed path (in which the ends are joined), thereby making it a loop. The flow of electric current is possible because of the closed circuit. An electric circuit can also be an open circuit in which the flow of electrons is cut because the circuit is broken. Electric current doesn't flow in an open circuit.

It is important to know about the basic parts of an electric circuit. A simple electric circuit contains a source, a switch, a load, and a conductor. The functions of these parts are:

Cell: It is used as a source to supply electric current.

Load: It is a resistor. It is basically a light bulb, which glows when the circuit is turned on.

Conductors: Copper wires are used as conductors with no insulation. One end of the wire carries current from the power source to the load, and the other end from the to the power source.

Switch: It is a part of the circuit which controls the supply of current in the circuit. It is used to open or close the circuit.

Electric current and voltage are the two basic features of an electric circuit. Electric circuit analysis is a process in which current and voltage are determined in any element of the electric circuit.

The above figure represents a simple electric circuit containing

● A battery of 30 V (voltage)

● A carbon resistor of 5 kΩ (resistance)

Due to the complete circuit, current I flows through the circuit, and a potential drop of V volts is developed across the resistor.

### Types of Electric Circuits

There are two types of electric circuits.

● Series circuit.

● Parallel circuit.

### Series Circuit

In a series circuit, there is only one path for the flow of electrons. The entire circuit is closed or open at the same time. No current flow in the circuit in case of a circuit break because the entire circuit is open; this is the major disadvantage of a series circuit. For example, if many light bulbs are connected in a series circuit, then if one light bulb goes out, the others will also turn off.

### Parallel Circuit

In a parallel type of electric circuit, different parts of the circuit are connected across different branches. Hence, electron flow occurs in several parts. If in one path a circuit break occurs, electric current still flows in other paths. Household wiring of appliances are based on parallel circuits, so if one light bulb goes down, the other will still flow.

### Domestic Electric Circuit

The above figure represents domestic circuit diagram

• The electric power that we receive in our houses is by the main supply, commonly called mains.

• It is supplied by either overhead cables or by underground cables.

• There are 3 types of wires in domestic circuits and these are Earth Wire, Live Wire, and Neutral Wire.

• Earth Wire: The earth wire is generally green in color. It is connected with a metal plate buried in the ground near the house, to provide safety for the gadgets and appliances which have a metallic body. When a charge leak occurs in the metallic body, the charges are transmitted to the ground to prevent shocks and damage.

• Live Wire: It is the positive conductor or wire which is generally red in color.

• Neutral Wire: It is the negative conductor or wire which is generally black in color.

• The potential difference (or voltage) which is supplied in our country is 220V.

• The electric current of our house is first passed through a circuit called a Fuse. If any high voltage, overloading, voltage fluctuation or short circuit occurs, the fuse melts thereby restricting the current supply and preventing the high voltage from reaching the electric appliances.

• These wires are passed to different electric appliances of the house through the meter board.

• Generally, 2 types of electric circuits are used for household use:

• 15 A: Appliances that have higher power ratings. ( like geysers, ACs, refrigerators)

• 5 A: Appliances that have lower power ratings. ( like TV, fans, bulbs)

### Precautions While Using Electric Circuits

● Always use good quality wires which have proper insulation and thickness, for household wiring. Install products like plugs, switches, and sockets that have an ISI mark in them for better use of electrical appliances.

● The connections of the wires should be tight and completely insulated.

● You should always switch off the mains supply before starting any repair work of the electric circuit.

● If any short circuit or shock occurs, switch off the mains supply at first. Then try to totally insulate the person who has received an electric shock. Do not touch him directly.

● While earthing or installing a fuse for the household electric circuits, you should take precautions.

1. State Some Properties of Electric Circuit

Ans- The basic properties of an Electric Circuit are:

● An electric circuit is always a closed path.

● An electric circuit contains at least one power supply which provides the flow of electrons.

● The electric elements contain controlled and uncontrolled sources of energy, resistors, capacitors, inductors, etc.

● The flow of electrons in an electric circuit occurs from the negative terminal to the positive terminal.

● The conventional direction of the flow of electric current is from the positive to the negative terminal.

● The flow of current leads to a potential drop across various electric elements.

2. Give Some Electric Circuit Examples

Ans- a. The potential of live wire is

i. 0 V

ii. 300 V

iii. 220 V

iv. 1000 V

Ans- iii. 220 V

From electric poles located near our house, two insulated wires L and N are supplied to our house. L-wire is called the live wires and N-wire us called the neutral wire. The potential of the neutral wire is 0 volts, and that of live wire is 220 volts.

b. A series circuit usually includes a 9-V power source, and four resistors having resistances of 1, 1.5, 2, and 4.5 Ω. What is current?

The total resistance in this circuit will be 1.5 + 4.5 + 2 + 1 = 9 Ω.

The current flow calculated by the formula

I = V/Rtot = (9 V/9 Ω) = 1 A.