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Basic Laws of Electrical Circuits

In circuit electronics, three fundamental laws are crucial for understanding how electrical circuits operate:

Ohm's Law

  • Formula: V = I * R

Ohm's Law defines the relationship between voltage (V), current (I), and resistance (R) in a circuit. It states that the voltage across a resistor is directly proportional to the current flowing through it, with resistance being the constant of proportionality. This law is foundational for analyzing electrical circuits and understanding how components behave.

Kirchhoff's Current Law (KCL)

KCL states that the total current entering a junction or node in a circuit must equal the total current leaving the node. Essentially, it reflects the principle of conservation of charge, ensuring that all the current flowing into a node must flow out.

Kirchhoff's Voltage Law (KVL)

KVL states that the sum of all voltages around any closed loop in a circuit must equal zero. This law is based on the conservation of energy, implying that the total potential differences (voltage drops) in a closed loop must sum to zero, as energy cannot be created or destroyed in the circuit.

These laws are the building blocks for analyzing and designing electrical circuits, from simple resistive circuits to complex electronic systems.

I-V Curves

Many of our examples will use a current vs. voltage plot. This shows how as you vary the voltage across a circuit what current will flow through the circuit.

By convention, voltage is usually on the lower horizontal axis and current is on the left vertical axis.

Here is a basic circuit with a power supply and a resistor: Resistor Circuit

When we vary the Input Voltage we get the following plot:

IV Plot

Here is an interactive version of this plot:

Resistor Current-Voltage MicroSim

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