# Electric Field and Circuits

1. Jun 2, 2013

### Jimmy87

I was reading my physics textbook which says that a current carrying wire has no net charge and thus no electric field because the electrons cancel the protons in the atoms of the wire. Would there not be an electric field created by the battery as you have a positive and a negative terminal? As I thought this is what creates a voltage and makes the charges move? So is there an electric field in the space in and around the circuit but it is created by the battery not the wires? Would this field be inside or outside the wires of the circuit or both? Any help is much appreciated.

2. Jun 2, 2013

### Staff: Mentor

There are electric fields, but outside the circuit elements you can usually neglect them.

3. Jun 2, 2013

### technician

When can you not neglect them ??

4. Jun 2, 2013

### yungman

Remember the wire is assumed to be very good conductor, even though you have current through the wire, there is no voltage drop across the wire, so there is no electric field along the wire.

The circuit must have some resistive components that drop the voltage of the battery, that has nothing to do with the wires. Yes, if voltage developed on the resistive load, the wire at the +ve terminal is going to rise above ground ( if the -ve terminal of battery is grounded) and yes, there will be electric field coming out perpendicular to the wire. But I don't think that's what you are talking about.

In real life, there is always small resistance across the wire, that cause a slight voltage drop across the wire and a little horizontal electric field along the wire exist.

5. Jun 2, 2013

### Staff: Mentor

For antennas and for some high-frequency applications.

6. Jun 2, 2013

### yungman

I don't think you can neglecting electric ( more EM) field in frequency above a few MHz which, applies to a lot of circuits these days. Particular above frequency that the structure becomes a significant fraction of a $\lambda$. That's when voltage difference becomes apparent between two point of the line ( wire). This is a totally different mechanism from voltage drop due to resistance along the wire. But I don't think this is what OP is asking.......I hope. Or else, that's another whole can of worms.

Last edited: Jun 2, 2013