# Quick Quick electrical current concept question

1. May 29, 2012

### StephenD420

Hello all

I have a quick concept question concerning electrical current. For real life components, would they only draw the current needed......In other words, if the current of a voltage source of 12V happened to be 500A going through a resistor of 2 ohms, would the resistor pull only 6A or would it pull the 500A from the power supply?

Thanks.
Stephen

2. May 29, 2012

### LawrenceC

I = V/R. With 12 volts and 2 ohms, the current is not 500 amps.

3. May 29, 2012

### Staff: Mentor

Two essential types of sources you'll run into are voltage sources and current sources. In its ideal form a voltage source will produce a fixed voltage no matter what, and will generate ANY amount of current required to maintain that fixed voltage no matter what the source is connected to. An ideal current source, on the other hand, maintains a fixed current flow no matter what, and will generate ANY amount of voltage required to maintain that fixed current flow no matter what the source is connected to.

A typical real-life voltage supply will be rated for a given fixed voltage which it can maintain up to some maximum current that it is capable of producing. It sounds like the source you described is of this variety (12V at a maximum of 500A). Use Ohm's law to determine the actual current it must produce for that fixed voltage when it's connected to a given resistor load.

4. Apr 2, 2013

### malemdk

The current depends only on the resistance and voltage in your case it is 6A ,the current source can supply maximum current of 500A but the circuit draws only what it really want

5. Apr 2, 2013

### CWatters

It is better to write that as...

"If a voltage source of 12V (capable of delivering 500A) is connected to a 2 Ohm resistor, would the resistor draw 6A or 500A?"