Electric Circuit

An electric circuit is a closed loop through which electric current flows in a definite direction. It consists of various electrical components, each performing a specific function, where the source supplies electrical energy and the return path completes the circuit.

The above electric circuit consists,

• Electric bulb
• Wire (Conductor)
• A battery

When only one terminal of the battery is connected to the bulb, it does not glow. The bulb lights up only when the other terminal is also connected, and the circuit is completed. This shows that electric current flows only in a complete circuit. Loose or improper connections can cause electric fires, and water should never be used to extinguish them, as it may cause electric shock.

Types of Electric Circuits

Many types of electrical circuits are used in our daily lives. Some of the most common electric circuits are:

• Open Circuit
• Closed Circuit
• Short Circuit
• Series Circuit
• Parallel Circuit

1. Open Circuit

A circuit in which the switch is open and current does not flow through the circuit is called an open circuit.

2. Closed Circuit

A circuit in which the switch is closed and current flows through the circuit is called a closed circuit.

3. Short Circuit

Whenever the current in the circuit follows a shorter path rather than following its usual path, a short circuit happens. The consequence of the short circuit is that the electrical board or the electrical system catches fire. The major cause of the electric fire is the short circuit. The image below shows the fire caused by the short circuit.

4. Series Circuit

If all the resistors are connected in a series combination, we say that it is a series circuit.

5. Parallel Circuit

If all the resistors are connected in a parallel combination, we say that it is a parallel circuit.

For more, Series and Parallel Resistance

Domestic Electric Circuit

The circuit used in our home is called a Domestic circuit and is specifically made for domestic purposes. Various components of the domestic circuit are,

Mains Supply: The electric power we receive in our houses is called the main supply.

Cables: Electric power is supplied by cables, which are either open or underground.

There are three types of wires used in domestic circuits, which are 

• Earth Wire
• Live Wire
• Neutral Wire

Potential Difference (or Voltage): In our country, the current is supplied at 220V in domestic circuits.

Electric current is passed to our house at 220 volts through a circuit called a Fuse. If the supplied voltage varies a lot compared to the allowed voltage, the fuse wire breaks and stops the flow of current in the circuit. The current then passes through the meter board.

From the meter board, generally, two types of current are supplied to the circuit.

• 15 Amp current: Used for high-power appliances such as geysers, air conditioners, refrigerators, electric motors, etc.
• 5 Amp current: Used for low-power appliances such as televisions, fans, bulbs, computers, smartphones, etc.

Electric Circuit Symbols

Electric circuits are represented using standardized symbols. Some of the important symbols used in physics for drawing electric circuits are:

Simple Circuit

A simple circuit consists of a power source, conductors, a switch, and a load. Some of its basic components are:

• Cell: It is the power source that provides the potential difference in the electric circuit.
• Load: A resistor that consumes current in a circuit is called the load. Generally, a load is a bulb.
• Conductors: Copper conductors that conduct electricity in a circuit are called conductors.
• Switch: A device that controls the incoming flow of current in an electric circuit is called a switch.

Electric Circuit Formula

Related Articles:

• Direct Current Circuit
• What is Ohm's Law
• Power in AC Circuit
• Heating Effect of Electric Current

Solved Problems

Question 1: A charge of 600 C flows through a conductor in 5 minutes. Find the electric current.

Solution: Given: Q = 600 C

t = 5 min = 300 sec

Electric Current:

I = \frac{Q}{t}

= I =\frac{600}{300}

Electric current = 2 A

Question 2: An electric bulb operates at 220 V and draws a current of 0.5 A. Find the power consumed.

Solution: Given: V = 220 V

I = 0.5 A

power Formula: P = V.I

P = 220 × 0.5 = 110 W

Power Consumed = 110 W

Question 3: Two resistors of 6 Ω and 3 Ω are connected in parallel to a 12 V supply. Find equivalent resistance and total current drawn.

Solution: Equivalent resistance in parallel

\frac{1}{R_{eq}} = \frac{1}{6} + \frac{1}{3}

\frac{1}{R_{eq}} = \frac{1+2}{6} = \frac{3}{6}

R_eq = 2 Ω

Total Current: I = \frac{V}{R_{eq}}

\frac{12}{2} = 6 A

Equivalent resistance = 2 Ω and Total current = 6 A

Question 4: Three resistors of 2 Ω, 4 Ω, and 6 Ω are connected in series to a 12 V battery. Find equivalent resistance and current in the circuit.

Solution: Equivalent resistance in series:

R_eq ​= R₁​ + R₂ ​+ R₃

R_eq = 2 + 4 + 6 = 12 Ω

Current using Ohm’s Law:

I = \frac{V}{R_{eq}}

\frac{12}{12} = 1 A

Equivalent resistance = 12 Ω and Current = 1 A

Question 5: A copper wire has a length of 2 m, a cross-sectional area of 1 × 10^⁻⁶ m², and a resistivity of 1.7 × 10^{⁻⁸ Ωm.} Find its resistance.

Solution: Formula:

R = \frac{\rho l}{A}

Substituting values:

R = \frac{1.7 \times 10^{-8} \times 2}{1 \times 10^{-6}}

Resistance of the wire = 0.034 Ω

Unsolved Problems

Question 1: A charge of 900 C flows through a conductor in 3 minutes. Find the electric current flowing through the conductor.

Question 2: An electric circuit has a resistance of 10 Ω, the equivalent, and a current of 2 A flows through it. Find the potential difference across the circuit.

Question 3: Four resistors of 3 Ω, 5 Ω, 7 Ω, and 10 Ω are connected in series to a 50 V battery. Find the a, current flowing through the circuit and the stop power consumed by the circuit.

Question 4: Three resistors of 4 Ω, 6 Ω, and 12 Ω are connected in parallel across a 24 V supply. Find equivalent resistance and total current drawn from the source.

Question 5: A wire has a length of 5 m and a cross-sectional area of 2 × 10^{⁻⁶ m.} If the resistivity of the material is 1.6 × 10^⁻⁸ Ωm, find the resistance of the wire.

Question 6: An electric heater operates at 200 V and draws a current of 1.5 A. Find the electrical power consumed by the heater.