Current Electricity

What is Current Electricity?

Current electricity refers to the flow of electric charge through a conductor. This flow is driven by a potential difference between two points and is known as an electric current. The electric current can be either direct current (DC) or alternating current (AC).

Electric current is measured in amperes (A) and is driven by the potential difference or voltage between two points in a circuit. The unit of potential difference is volt (V), and the unit of current is ampere (A).

Ohm's Law

Ohm's law states that the current passing through a conductor is directly proportional to the potential difference (voltage) across it, provided the temperature remains constant. It can be mathematically expressed as:

V = I × R

Where:

• V is the voltage across the conductor (in volts).
• I is the current flowing through the conductor (in amperes).
• R is the resistance of the conductor (in ohms).

Resistance and Its Factors

Resistance is the opposition that a conductor offers to the flow of electric current. The resistance of a conductor depends on the material, length, cross-sectional area, and temperature of the conductor.

The resistance can be calculated using the formula:

R = ρ × (L / A)

Where:

• ρ is the resistivity of the material (in ohm meters).
• L is the length of the conductor (in meters).
• A is the cross-sectional area of the conductor (in square meters).

Current and Voltage in Series and Parallel Circuits

In a series circuit, the current is the same throughout, but the voltage is divided among the resistors. In a parallel circuit, the voltage is the same across all components, but the total current is the sum of the currents through each branch.

Series Circuit:

For resistors in series, the total resistance is the sum of individual resistances:

R_total = R₁ + R₂ + R₃ + ...

Parallel Circuit:

For resistors in parallel, the total resistance is given by:

1 / R_total = 1 / R₁ + 1 / R₂ + 1 / R₃ + ...

Power in Electric Circuits

Power in an electrical circuit is the rate at which electrical energy is converted into another form of energy, such as heat, light, or mechanical energy. The power can be calculated using the following formula:

P = V × I

Where:

• P is the power (in watts).
• V is the potential difference (in volts).
• I is the current (in amperes).

Kirchhoff’s Laws

Kirchhoff’s laws help analyze complex electrical circuits. There are two laws:

• Kirchhoff’s Current Law (KCL): The sum of currents entering a junction is equal to the sum of currents leaving the junction.
• Kirchhoff’s Voltage Law (KVL): The sum of the potential differences (voltages) around any closed loop in a circuit is zero.

Previous Year Questions

• RRB JE 2016: In a series circuit, how is the total current related to the resistance?
• The total current is inversely proportional to the total resistance.
• SSC JE 2017: What is the total resistance of two resistors, 10Ω and 20Ω, connected in parallel?
• 5Ω
• HSSC JE 2018: If the power supplied to a circuit is 120W and the voltage across the circuit is 12V, what is the current flowing through the circuit?
• 10A

Conclusion

Current electricity is an essential concept in electrical engineering and physics. It forms the basis for understanding electrical circuits, power generation, and many technological applications. By mastering Ohm's law, Kirchhoff's laws, and the concepts of resistance, power, and circuits, you will gain a strong understanding of how electrical systems work.