Is there an electric field in a circuit and how is it created?

In summary, the electric field around a current carrying wire is created by the battery, not the wire.
  • #1
Jimmy87
686
17
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.
 
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  • #2
There are electric fields, but outside the circuit elements you can usually neglect them.
 
  • #3
mfb said:
There are electric fields, but outside the circuit elements you can usually neglect them.
When can you not neglect them ??
 
  • #4
Jimmy87 said:
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.

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
technician said:
When can you not neglect them ??
For antennas and for some high-frequency applications.
 
  • #6
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:

1. What is an electric field?

An electric field is a region of space surrounding an electric charge where another charge experiences a force. It is represented by electric field lines and is measured in units of volts per meter (V/m).

2. How is an electric field created?

An electric field is created by an electric charge. Positive charges create outward-pointing electric field lines, while negative charges create inward-pointing electric field lines. The strength of the electric field is directly proportional to the magnitude of the charge creating it.

3. What is the difference between an electric field and an electric circuit?

An electric field is a physical phenomenon that describes the interaction between electric charges, while an electric circuit is a system of interconnected components that allows the flow of electric current. Electric fields exist in the space surrounding an electric circuit, and they play a crucial role in the behavior of the circuit.

4. What is the relationship between electric potential and electric field?

Electric potential is the amount of work required to move a unit of charge from one point to another in an electric field. The strength of the electric field is directly related to the change in electric potential over a given distance. In other words, the electric field is the gradient of the electric potential.

5. How does the presence of conductors and insulators affect an electric field?

Conductors, such as metals, have free electrons that can move easily, allowing for the flow of electric current. In contrast, insulators, such as rubber or plastic, do not have free electrons, so they do not allow for the flow of electric current. Therefore, the presence of conductors and insulators can alter the strength and direction of an electric field.

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