DC CIRCUITS

PRERNA FOR IAS

DC CIRCUITS

1. Electric Current

Electric current is the rate at which electric charge flows through a conductor. It is represented by the symbol I and is calculated using the formula I = Q/t, where Q is the electric charge and t is the time taken. The SI unit of electric current is the Ampere (A). Current flows when there is a potential difference between two points in a circuit. Conventional current is considered to flow from the positive terminal to the negative terminal of a source. Electric current is fundamental to all electrical devices and is essential for powering homes, industries, and electronic systems.

2. Ohm’s Law

Ohm’s Law describes the relationship between voltage, current, and resistance in an electrical circuit. It states that at constant temperature, the current flowing through a conductor is directly proportional to the voltage applied across it. The formula is V = IR, where V is voltage, I is current, and R is resistance. This law helps engineers and electricians calculate unknown electrical quantities in circuits. Ohm’s Law is one of the most important principles in electrical engineering and is widely used in designing and analyzing electrical and electronic devices.

3. Resistance

Resistance is the property of a material that opposes the flow of electric current. It is represented by R and measured in Ohms (Ω). The resistance of a conductor depends on its resistivity, length, and cross-sectional area. The formula is R = ρL/A, where ρ is resistivity, L is length, and A is area. Longer conductors have greater resistance, while thicker conductors have lower resistance. Resistance plays an important role in controlling current flow and protecting electrical components. Different materials have different resistivities, making them suitable for various electrical applications.

4. Resistors in Series

When resistors are connected one after another in a single path, they are said to be connected in series. The total resistance is the sum of all individual resistances: Rs = R₁ + R₂ + R₃ + .... In a series circuit, the same current flows through each resistor because there is only one path available. However, the voltage is divided among the resistors according to their resistance values. Series connections are commonly used in electrical circuits where controlled current flow is required. Understanding series circuits is important for solving circuit problems and designing electrical systems.

5. Resistors in Parallel