Ohm’s Law – V = I × R

1. Introduction

Ohm’s Law describes the relationship between voltage (V), current (I), and resistance (R). It states that the current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance. This is the foundation of all circuit analysis.

2. Basic Formula

The basic form of Ohm’s Law is:

V = I × R

From this, you can rearrange the formula to find the unknown quantity:

I = V / R
R = V / I

3. Example

Given a 12V power supply and a 6Ω resistor:

I = V / R = 12 / 6 = 2A

Therefore, the current flowing through the resistor is 2 amperes.

4. Practical Applications

• Calculate a current-limiting resistor for an LED.
• Estimate current consumption for an Arduino or sensor circuit.

5. Practice Exercise

Question: A 9V supply powers a 3Ω resistor. Find the current and power dissipation.

Solution:

I = V / R = 9 / 3 = 3A
P = V × I = 9 × 3 = 27W

6. Additional Notes

Ohm’s Law applies strictly to linear components such as resistors. Non-linear devices (like diodes and transistors) do not follow a straight-line V-I relationship; instead, they exhibit a curved response.

7. Conclusion

Ohm’s Law is the foundation of electrical circuit analysis. Once you understand how voltage, current, and resistance interact, you can analyze and design virtually any basic circuit.

References

• Thomas L. Floyd, Electronics Fundamentals: Circuits, Devices, and Applications, Pearson, 2014.
• Allan R. Hambley, Electronics, Prentice Hall, 2000.

Keywords: Ohm’s Law, V=IR, voltage, current, resistance, electrical circuit, basic electronics