400 Ohms Between 5v Positive And 5v Negative

400 Ohms Between 5V Positive and 5V Negative: A Short Circuit Explained

This article explains the implications of connecting a 400-ohm resistor between the positive and negative 5V rails of a power supply. In short: it's a bad idea and will likely result in a short circuit, potentially damaging your power supply or other components. This is because you're creating a direct path for current to flow, bypassing any intended circuitry. Let's break down why.

Understanding the Basics

A 5V power supply provides a voltage difference of 5 volts between its positive (+) and negative (-) terminals. This voltage difference drives current through a circuit. A resistor, like the 400-ohm resistor in question, limits the flow of current. Ohm's Law (V = IR) governs this relationship: Voltage (V) equals Current (I) multiplied by Resistance (R).

The Problem: Calculating the Current

With a 5V difference and a 400-ohm resistor, we can calculate the current:

I = V/R = 5V / 400Ω = 0.0125A = 12.5mA

While 12.5mA might seem small, it's still significant. This current will flow continuously through the resistor, generating heat. The amount of heat depends on the power dissipated by the resistor, calculated using the formula P = I²R:

P = (0.0125A)² * 400Ω ≈ 0.0625W

This power dissipation, while seemingly low, can still overheat a small resistor, potentially causing it to burn out or even become a fire hazard. More importantly, placing a resistor directly across the power supply rails is generally not how circuits are designed.

Why This is a Bad Idea

Connecting a resistor directly between the positive and negative rails effectively creates a short circuit, albeit a limited one due to the resistor. Here's why this is problematic:

• Wasted Power: The power supply is constantly supplying energy that is converted to heat in the resistor, which is inefficient and wasteful.
• Overheating: The resistor will overheat, potentially leading to its failure and possibly posing a safety risk.
• Power Supply Strain: Depending on the power supply's design and current capacity, this constant load could strain the power supply, potentially leading to its damage or malfunction. Smaller power supplies are more vulnerable to this.
• Incorrect Circuit Operation: If this resistor is part of a larger circuit, it will severely disrupt the intended function of that circuit.

What Should You Do Instead?

The correct approach depends entirely on the intended use case. Resistors are crucial components in electronic circuits, but they are used strategically to control current flow within specific paths, not as a direct connection between power rails. If you're working on a circuit, refer to the circuit diagram and understand the role of each component before connecting anything.

In conclusion, connecting a 400-ohm resistor directly between the positive and negative 5V rails is not a recommended practice. It creates an inefficient and potentially damaging short circuit. Always carefully design and understand your circuit before connecting components. Understanding basic electronics principles and following circuit diagrams are essential to avoid such issues.