Many beginners in electronics think that current decreases after passing through a resistor. At first glance, it sounds logical, after all, a resistor “resists” current, right?
But here is the truth: the current before and after the resistor is exactly the same. Let’s break this misconception with a simple real-world example and an analogy that you will remember every time you see a resistor in a circuit.
The Common Misconception:
You have probably heard someone say:
At first, that sounds logical, but it is actually not true.
But no that is not how it works.
In a series circuit, the same current flows through every component, including the resistor. The current entering the resistor is exactly the same as the current leaving it.
What actually changes across the resistor is the voltage, not the current at that point.
what does the resistor actually do🤔?
A resistor doesn’t “consume” current. Instead, it controls how much current can flow through the entire circuit.
Imagine electricity like water flowing through a pipe. If one part of the pipe becomes narrower, the overall flow of water decreases.
But here is the key point:
The amount of water entering that narrow section is the same as the amount leaving it every second.
That is exactly what happens in an electrical circuit.
A resistor limits the flow of current, but the current before and after the resistor stays the same. Actually, resistor drops the voltage, not the current.
Let’s Take a Real Example:
Imagine you have a 9V battery connected to a small LED bulb.
If you connect the LED directly to the battery, it will burn out instantly, because too much current will rush through it.
So, you add a resistor in series with the LED.
Here is what happens:
- The resistor limits how much current the battery can push through the circuit.
- The same current flows through both the resistor and the LED (since they’re in series).
- What changes is the voltage, part of the battery’s voltage drops across the resistor, and the rest appears across the LED.
In simple words, the resistor doesn’t stop the current, it just controls its flow. The current before and after the resistor stays exactly the same, but the voltage is shared between the resistor and the LED.
Understanding the above example with Ohm’s Law:
Ohm’s Law states:
I = V / R
If you increase the resistance “R”, the total current “I” decreases.
Short Summary:
| Concept | What Happens |
|---|---|
| Current entering the resistor | Same as current leaving the resistor |
| Voltage across the resistor | Drops depending on resistance |
| Effect on the circuit | Limits total current flow |
| Energy | Converted to heat (in the resistor) |