Unit 2 D.C Circuits

 

1. What is a DC Circuit?

A DC circuit is an electrical circuit where the current flows in one direction only, maintaining a constant polarity. Direct current (DC) is characterized by a steady and constant flow of electric charge in a single direction. DC circuits are commonly found in batteries, electronics, vehicles, and many other applications.

2. Basic Components of a DC Circuit:

• Voltage Source (E): Provides the electromotive force (EMF) or voltage necessary to create current flow. This can be a battery, DC power supply, or any source of DC voltage.
• Load: The component in the circuit that consumes the electrical energy, such as a light bulb, motor, resistor, or any device using the electricity.
• Wires and Conductors: Conductors like copper wires connect the components and allow the flow of electric current.
• Switches: Control the flow of current by opening or closing the circuit path.

3. Key Definitions:

• Voltage (V): The electrical potential difference between two points in the circuit. It represents the "push" or force that drives current through a circuit. Measured in Volts (V).

• Current (I): The flow of electric charge through a conductor. It represents the rate of flow of charge. Measured in Amperes (A).

• Resistance (R): The opposition to the flow of electric current in a circuit. It determines how much current will flow for a given voltage. Measured in Ohms (Ω).

• Ohm's Law: The fundamental relationship between voltage, current, and resistance in a DC circuit. It states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) between them:

  I = V / R

This equation can also be rearranged to solve for voltage (V) and resistance (R):

V = I • R 

R = V / I

4. Series DC Circuits:

In a series circuit, components are connected end-to-end, forming a single path for current flow. The same current flows through each component, and the total resistance is the sum of individual resistances. Voltage across each component adds up to the total supply voltage.

• The formula for total resistance in a series circuit (R_total) is the sum of individual resistances:

  R_total = R1 + R2 + R3 + ...

• The formula for total voltage in a series circuit (V_total) is the sum of individual voltages:

  V_total = V1 + V2 + V3 + ...

5. Parallel DC Circuits:

In a parallel circuit, components are connected across each other, forming multiple paths for current flow. Voltage across each component is the same and equal to the supply voltage. The total resistance in a parallel circuit is calculated differently:

6. Power in DC Circuits:

• Power (P): The rate at which work is done or energy is transferred in a circuit.

The formula for power in a DC circuit is:

7. Kirchhoff's Laws:

• Kirchhoff's Current Law (KCL): The total current entering a junction (or node) in a circuit must equal the total current leaving the junction. This is based on the principle of conservation of charge.
• Kirchhoff's Voltage Law (KVL): The total voltage around any closed loop in a circuit must equal the total voltage drop. This is based on the principle of conservation of energy.
  
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