Is the current lower after a resistor?

Ohms law cartoon


It is not.

It’s a common misunderstanding.

But let me make it clear:

The current after a resistor is the exact same as it was before the resistor.

“But doesn’t the resistor reduce the current?”

Yes, it does.

A circuit always has a bit of resistance, no matter if it has resistors or not in it.

Even wires have a little bit of resistance.

So let’s imagine a circuit – any kind of circuit – and say that its current is 1 ampere.

If you now add a resistor in series into this circuit – the current of the circuit will be smaller than it was.

So yes, the resistor does reduce the current.

(But the current flowing into the resistor is still the same as the current flowing out.)

This is one of the mindset shifts a beginner has to go through when learning electronics.

But after a few examples and a bit of practice, this becomes obvious. And it becomes much easier to understand what all the circuits actually do.

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10 thoughts on “Is the current lower after a resistor?”

  1. thanks dog this is really helpful. this really clears up the mess In a way my teachers or textbooks or youtubevideos couldn’t do, and I’m very thankful for that. peace man

    • The current that goes into the resistor is the same as the current coming out of the resistor.

      The current flowing in the circuit with a resistor is smaller than the current in the circuit without a resistor.

    • If we increase the resistance of a circuit the equivalent current decreases ie the current flowing in the complete circuit will be decreased. so the current flowing into the resistor is already reduced because current is inversely promotional to resistance and remains unchanged as it moves out of the resistor

  2. Case 1 :- Let a circuit in which we didn’t add any external resistor , then the measure of current is 4A and battery is of 7v. B. . . Case2:- now add a resistor then the current flow and reach where there is resistor, I think that current before resistor is 4A, and after passing through resistor current should reduce . But according to law it is not correct because current is same in a circuit. .explain it how it can possible?

    • Think of a hose with water flowing out of it. Let’s say you have 1 litre of water flowing out of the hose per second.

      Next, you squeeze the middle of the hose so that less water flows out. Let’s say 0.5 litres of water per second flows now. So after the point of the hose where you are squeezing, you know that 0.5 litres of water per second is flowing.

      But how much water is flowing in the hose before the point where you squeeze?

      It must also be 0.5 litres of water per second. It’s impossible that more or less water (per second) flows before the point where you are squeezing.

      It’s the same with electricity.

      You can think of wires as completely filled with electrons at all times. Even when not connected to a battery. When you connect to a battery, the battery starts pushing in electrons. But one electron going in, means that one electron must go out on the other end.

      The current that flows out of the plus is exactly the same as the current flowing back into the minus of the battery.

    • In a parallel circuit there are more than one path for the current to flow, so it will be different. But when you connect a resistor with an LED, you have to connect them in series for the resistor to have an effect on the LED current.

  3. How current flowing in resistor is same as in wire which it is connected and after the end of resistor, current is also same but at the same time current get smaller ?


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