First off, I'd like to say that I am completely new to electronics and the way circuits work, so this may be a really dumb question.

I've tried searching Google but I can't really find what I'm looking for since I'm new to all this.

Basically, I'm trying to get a pencil graphite to produce some smoke.

When I connect one part of graphite to the +5V Arduino pin and other to ground, it smokes for a bit before Arduino's short-circuit protection kicks in.

The above works as expected, but when I connect it the same to the 9V battery as the source, the graphite barely warms up.

So my question is - why does Arduino's 5V make graphite smoke while the 9V battery doesn't?

  • 1
    \$\begingroup\$ Have you checked that the 9 V battery is full? \$\endgroup\$
    – Arsenal
    Nov 19 '19 at 15:15
  • \$\begingroup\$ The voltage is completely irrelevant. Show some schematics of how you connected these. \$\endgroup\$
    – Lundin
    Nov 19 '19 at 15:15
  • \$\begingroup\$ Yeah Arsenal, the battery's brand new. Lundin, I connected them exactly the same, on a breadboard. \$\endgroup\$
    – Daniel
    Nov 19 '19 at 15:26
  • \$\begingroup\$ This is a bit strange. The actual wires could play a big role. If they are tiny in diameter, the resistance of the wires might be too high (do the wires get warm?). I would avoid using a breadboard with high currents as well (see this). The battery won't last long though, I'd give it a minute at maximum if it's really pumping out all the current it can, then it's dead. \$\endgroup\$
    – Arsenal
    Nov 19 '19 at 16:04
  • \$\begingroup\$ get a 6volt "lantern battery" \$\endgroup\$ Nov 19 '19 at 16:07

A 9V battery can't provide much current due to it's internal resistance. Depending on what is powering the Arduino 5V, it can put out much more current than a 9V battery.

  • \$\begingroup\$ A fresh 9V block has an internal resistance of around 1.5 to 2 Ω, that gives a short circuit current of 4.5 to 6 A - certainly not for long at maximum a minute, typical Arduino 5V regulators are limited to 800 mA. \$\endgroup\$
    – Arsenal
    Nov 19 '19 at 15:59

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