# Why do we need to find the current?

I am beginner in electronics. What i came to know until now is that mostly we have to find the current in a circuit in our text books. I wonder what useful work we do after finding the current, dc current, current as a function of time, transient current , ac current. What do we do after findings these currents. I know this question would be offensive to many of you here but as i am a beginner so kindly forgive me in advance.

• How else would you solve the rest of the circuit? Commented Feb 6, 2016 at 19:25
• Why do we need to solve the circuit ? Commented Feb 6, 2016 at 19:39
• So that you know how it behaves. Commented Feb 6, 2016 at 19:40
• If it's an exam question, why do we care about passing the exam? And if it isn't, why do we care whether the circuit works, starts fires, flattens batteries or costs too much to run?
– user16324
Commented Feb 6, 2016 at 19:47
• @Brian: Give it up already. He's figured out those current and voltage calculations are just to keep undergrads busy so they don't notice that engineering on Earth is done by aliens, and that the humans are all slaves. It's amazing what you can make them do. Remember how we got them to watch Ice Road Truckers and listen to rap music? LOL! We'll need to do the brain suck on this guy and move on. Commented Feb 8, 2016 at 21:00

I consider this an entirely legitimate question, and certainly a sincere one coming from a beginner.

For me, the answer was "Don't bother calculating current until you care about it."

Instead, start building some simple circuits. The motivation will soon arise all on its own, possibly accompanied by whiffs of "magic smoke" as we call it.

For example, hook up an LED to a 9V battery with a 330 ohm resistor between the two. If it doesn't light, reverse the leads and see if that works. Search on the web to explain to yourself why it works one way and not the other.

Then take out the resistor and hook the LED up directly to the battery. Ask yourself why the LED doesn't work anymore after that (this has to do with current :). Search on the web for "led burnout" which perhaps leads you here: How can voltage burn out an LED?

If you don't have electronic components available, take some out of old electronics and/or download a free simulator like LTspice and make simple circuits there.

All these motivations to calculate and understand arose for us in the course of building things. I recommend the same approach to you if the electrical engineering spirit calls to you. If not, find something that does call to you and do that :)

• A 9V battery might not be able to burn out an LED, depending on the battery and the LED. Commented Feb 6, 2016 at 23:38
• thanks alot @scanny for the appreciation and guidance. from your answer the conclusion that i made until now is its important to analyse the circuit and to find the value of current or to know that how much the current a circuit or a component is taking to work properly. at more or less current circuit or components may not work good. am i right ? yes you are right i will have to built circuit manually for better understanding. Commented Feb 7, 2016 at 8:00
• @hurchuchu -- Current is absolutely fundamental to electronics; being the flow of electrons, it's either not turned on or not electronic if there's no current. So you'll find it everywhere you go in electronics. It's associated with heating (wanted and unwanted), power, safety, signal fidelity, just everything. It's important for powering circuits, as you mention, but it also constitutes the signals that travel through those circuits, like music, telephone conversations, or control signals. In those cases, too much might cause distortion and too little may make the signal ineffective. Commented Feb 7, 2016 at 8:09

Knowing the current is very important in all practical circuits.

• Cable, wires and PCB tracks need to be sized to carry the current without excessive heating along the cable (due to resistance of the conductor).
• Fuses need to be sized to protect those cables from exceeding the maximum current.
• Generators, transformers and switches all need to be sized to supply the required current and switch it safely.