# Current source and EMF

I've been going through some materials, and I was reading about electric circuits. From what I read I figured that the electric current is dictated by the current source, and it's preserved(in the respectable branches) by the emf. Is that right? Or my feeling that I'm way off is true :)

Drakkith
Staff Emeritus
What do you mean by saying the current is preserved by the emf?

I meant something like this: Somewhere in the circuit a current source dictates the current, and for it to be continuous in the near branches the emf sets high/low potentials for the electrons to continue moving in the ones where the emf is set. But I don't think that it is right at all when I see it now.

And I guess I meant voltage source by emf :)

Drakkith
Staff Emeritus
I meant something like this: Somewhere in the circuit a current source dictates the current, and for it to be continuous in the near branches the emf sets high/low potentials for the electrons to continue moving in the ones where the emf is set. But I don't think that it is right at all when I see it now.

I'm not an expert on electric circuits, so maybe that's why I'm a little confused. What do you mean by "continuous in the near branches"?

I guess I don't mean anything, I just don't get the "jobs" of each in a electric circuit. If the question is: "What does a current source do in a circuit, and what does a voltage source do?", would be clearer to understand?

Drakkith
Staff Emeritus
I guess I don't mean anything, I just don't get the "jobs" of each in a electric circuit. If the question is: "What does a current source do in a circuit, and what does a voltage source do?", would be clearer to understand?

I think you are just using terms I am unfamiliar with lol.
I know that the voltage determines the current in a circuit, and that the configuration of the components on the circuit determines the amount of voltage and current in each part. The voltage source IS the current source.

With a basic circuit, when you apply a higher voltage you get a higher current, as I=V/R will tell you. (50v/2ohms=25 amps, whereas 100/2=50 amps)

Voltage source is denoted with E, and current source with I. Maybe referring to it as voltage generator, electric generator will clear something out. However, E=U=I*R [V], I= [A]. English is not my mother tongue so it's difficult for me to find the right terms.

The electrons in the circuit are pushed by the Electric field. And Voltage is related to the Electric field.

Drakkith
Staff Emeritus
Voltage source is denoted with E, and current source with I. Maybe referring to it as voltage generator, electric generator will clear something out. However, E=U=I*R [V], I= [A]. English is not my mother tongue so it's difficult for me to find the right terms.

I think I can explain the basics. They might not be 100% correct in the details, but it should be good overall.

The Electric Field generated by a source is denoted as E. For our purposes discussing circuits we can effectively ignore it. Simply knowing the voltage applied to a circuit is enough.

I is the value of the current, measured in amperes, not the current source. Current is caused by a difference in electric potential, which is measured in Volts. A generator doesn't produce current, it produces a different in electric potential which then produces the current based on the resistance of the circuit. Applying a voltage to the beginning of the circuit indroduces a force, the EMF, which then propegates down the circuit as electrons move away from that force.

That's the way I understand it. I hope that is correct.