Voltage, current, and resistance are the three basic “ingredients” of any circuit, and they are tied together by Ohm’s law, which says V=I×R. Understanding them with simple real-life comparisons makes the math much easier to remember.
What is voltage?
- Voltage is the “electrical pressure” that pushes charges through a circuit, measured in volts (V).
- A good analogy is water pressure in a tank pushing water through a pipe: more pressure means water “wants” to flow more strongly.
Real example
- A 9 V battery has more “push” than a 1.5 V AA cell, so it can drive more current through the same resistor or LED.
What is current?
- Current is the rate at which electric charge flows, measured in amperes (A).
- In the water analogy, current is like the amount of water flowing per second through a pipe.
Real example
- If an LED datasheet says it needs 10 mA, that means the LED wants 0.01 A of current for normal brightness.
What is resistance?
- Resistance tells how much a component opposes current, measured in ohms (Ω).
- In the water analogy, resistance is like a narrow section of pipe that makes it harder for water to flow.
Real example
- A resistor in series with an LED limits current so the LED does not burn out; a higher resistance value means less current.
How they work together (Ohm’s law)
Ohm’s law links them
- V=I×R
- I=V/R
- R=V/I
Real LED example
- You have a 9 V battery and an LED that drops about 2 V at 10 mA. The resistor must drop the remaining 7 V at 0.01 A, so R=7/0.01=700 ΩR=7/0.01=700 Ω (you’d pick the nearest standard value, like 680 Ω or 720 Ω).
Everyday-style examples
- Mobile charger
- The adapter output is something like 5 V or 9 V; that’s the voltage.
- The “2 A” or “3 A” rating is the maximum current it can safely supply.
- The phone’s internal circuits and components provide resistance that sets how much current actually flows at that voltage.
- Room light with a dimmer
- Mains voltage is nearly fixed, but a dimmer effectively changes the resistance or effective path so less current flows, making the bulb dimmer.
- Long thin wires on a PCB
- A long, thin trace has higher resistance than a short, wide one, so it causes more voltage drop when high current flows through it.
- That is why power traces on PCBs are made wider to keep resistance (and heat) low.
This is all about Understanding Voltage, Current, and Resistance, Thanks for reading.
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