# Electric Circuit

## Definition

A closed-loop or path of electrical components is called an electrical circuit. In an electrical circuit, the flow of electrons takes place. An electrical circuit comprises wires, a battery, switch, and other components to measure the current flowing. The source is where the electrical current starts to flow—the point where electrons or the current ends is known as a return.

Take an electric bulb, wire, electrical tape, and a battery. Connect all of them tightly and adequately. Notice what happens. When the circuit is complete, electrons flow from the battery to the bulb, generating an electrical current due to which the bulb lights up. This will happen only when the circuit is complete. If the circuit is not complete, the bulb will not glow.

In an electrical circuit, there must be a close loop and a positive-negative end for current flow. The current flow may be from positive to negative and vice versa, depending upon the type of electrical circuit.

Faulty electrical circuits may cause fire and damage to property and lives. One must not neglect any sparking or short-circuiting in the electrical circuit. Electrical appliances must be handled with care. Appliances with chemicals inside them must be taken extra care of. They may leak and cause more damage than short-circuiting or failure in electrical circuits.

## Types of circuit

• Closed-circuit – The circuit that is complete and the current flows through it is called a closed circuit.
• Open circuit – The incomplete or open circuit in which the current does not flow is called an open circuit.
• Series circuit – The circuit with only one flow of current path is called a series circuit. The entire circuit will be closed or open at the same time. No current will flow if it breaks at any point. Some components will receive a more considerable amount of current, and some will receive less current in this circuit.
• Parallel circuit – In this, different components of an electric circuit are connected in branches or parallel. The flow of current is different in different branches, but every component will receive electrical current. Even if one branch fails, the whole network will work. This is the advantage of parallel circuits over series circuits. The current may be less in this case than the series circuit.

## Electrical symbols

The following symbols are used to denote components in an electrical circuit.

## Properties of Electric Circuit

• It is always a closed path.
• An electric circuit contains at least one power supply providing current.
• The electric elements contain both controlled and uncontrolled energy sources, resistors, capacitors, inductors, etc.
• The flow of electrons 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.

## Simple circuit

A circuit that comprises only a power supply source, switch, load, and conductor is known as a simple circuit.

• Cell or battery – this is the power source.
• Load – also known as a resistor; it lights the bulb when the circuit is complete.
• Conductors – made of copper wires; one end is connected to the power supply, another is connected to the wire that sends the power to load.
• Switch – it is used to close or open a circuit.

## Formula of electric circuit

 Quantity Formula Notations Electric current I = Q/t I is the current  Q is the charge flow T is the time Resistance R = ρ (L/A) R is the resistance Ρ is the resistivity of the wire L is the length of the wire A is the area of the wire Voltage V = IR V is the voltage; it can also be potential difference Power P = E/t P is the power E is the energy gain or loss t is the time Series circuit Req = R1 + R2 + R3 +… Req is the equivalent resistance of the circuit R1, R2,… are the resistances placed in the series circuit Parallel circuit 1/Req = 1/R1 + 1/R2 + 1/R3 +… Req is the equivalent resistance  R1, R2,… are the resistances placed in the parallel circuit

## Precautions

1. Use good quality electrical components with proper insulation, thickness, and functioning. Install every component              properly and make sure they have good quality.
2. The connections must be made tight and insulated completely to prevent any shock.
3. Switch off the main power supply before repairing or doing any electrical work in the house.
4. In a short circuit, switch off the main power supply to prevent further damage to any other appliance. Do not touch any        appliance in case short-circuit occurs.
5. Do not touch any appliance with wet hands as wet hands increase conductive power, leading to shock or death.
6. Install earthing to prevent any appliance from damage and fluctuations.

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