Voltage and current

1. Jun 4, 2014

Jhenrique

In an eletric circuit, can exist nonzero voltage and zero current? Can exist zero voltage and nonzero current?

What the voltage make (in the sense of task/function/operation) in the circuit?
What the current make (in the sense of task/function/operation) in the circuit?

2. Jun 4, 2014

Matterwave

1. You can have non-zero voltage and zero current if there is insulating material (e.g. air) between the two points. This is the case, for example, on a Van de Graaff generator which has a high voltage due to static electricity (non moving electricity = no current).

2. If you have no voltage across a circuit element, then you don't have anything to drive a current. Conventionally speaking, from an electrical engineering standpoint, the answer is probably no. However, you can have charges (say free-floating charges) freely moving in a direction which would then be called a current. For example, in a cathode ray tube, you accelerate the charges over a short distance (using a voltage) and then they basically free-stream to the other side of the tube. During it's free-stream period, there's no voltage difference, but there's a current.

Voltage is the potential energy (per unit charge) stored between a configuration of charges. This potential energy is what can accelerate charges from one place to another.

Current is just the movement of charges (how much charge passes a point in space per unit time).

3. Jun 4, 2014

Jhenrique

Good explanation! :D

4. Jun 5, 2014

cabraham

Superconductors have non-zero current w/ zero voltage. Either one can exist w/o the other under static conditions (not varying w/ time). Under dynamic conditions, you can't have one w/o the other. BTW, voltage is not what "drives current". A power source which translates energy from one form to another is what makes this happen, i.e. battery, generator, etc.

Claude