# Transistors, Current, Voltage, and Power [closed]

I was wondering how charge works. I know the majority charge carriers is electrons, yet current is the direction positive charge flows, which seems to be opposite electrons. I need to understand this to understand how BJT's work. If anyone could also explain voltage and power and tie it into transistors, that would be great. I've been trying to understand this for like a week and I'm only 15 so if I'm completely wrong please just correct me.

## closed as too broad by Andy aka, PeterJ, Daniel Grillo, Null, Michael KarasSep 20 '15 at 4:25

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Far too broad - break your question down into simpler pieces and do some searching on EE to find some of the answers about things. – Andy aka Sep 15 '15 at 7:19

You've asked (or implied) three questions that aren't really that closely related, so I'll only be able to discuss each one very briefly.

I know the majority charge carriers is electrons

This is not correct.

In metals, current is carried by free electrons.

In other materials, there are lots of other possibilities.

yet current is the direction positive charge flows, which seems to be opposite electrons.

This is correct. If electrons were flowing from left to right, we'd say "There's a current flowing from right to left."

For the most part, the best way to deal with this is to simply forget about electrons. Essentially all circuit design work can be done without worrying about electrons and only thinking about current.

If anyone could also explain voltage and power and tie it into transistors, that would be great.

If a current flows in to a device at a high voltage node and out at a lower-voltage node, then energy is being delivered to the device. If current flows into a device at a low-voltage node and out at a higher-voltage node, then the device is delivering energy to the rest of the circuit. Since transistors don't produce energy, you'll (just about) always find that they work the first way, consuming energy from the rest of the circuit.

Power is just the rate of energy being moved from one place to another. For example, if a transistor absorbs (and converts to heat) one joule of energy per second, we say it is consuming one watt of power.

Voltage is connected to this by the mathematical relation:

$$P = I V$$

The power consumed (or delivered) is equal to the product of the current through a device and the voltage difference between the terminals that the current flows in and out of.

• Thanks for the answer. Is voltage energy per charge or the push of current? – user2455722 Sep 15 '15 at 10:11
• @user2455722, it's both. Force and energy are intimately related. When you put a particle somewhere where there's a gradient in the potential, meaning it would take less energy to be "there" than "here", then that particle experiences a force towards "there". – The Photon Sep 15 '15 at 15:30