I have a power source connected to a resistor in series. I am asked, "what is the electromagnetic field in the circuit?"
I know there is a magnetic field due to the moving current but is there an electric field also?
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An electromotive source in a circuit produces an electric field $\vec{E}$, pointing towards, from higher to lower potential points.
In laymen's terms, you can think electric field as some "pushing agent" that pushes electrons (albeit in opposite directions because of the negative charge of electrons). The electric field is always generated whenever there is a potential difference between the points.
Potential difference can be thought of as a "hill" and we can go down the hill by exchanging potential for kinetic energy (however this analogy is reverse for electron particles because of negative charge).
For rigourous explanation, we can find $\vec{E}$ from: $$\vec{j}=\sigma \vec{E}$$
The $\vec{j}$ is the current density at a point which can be thought of as the product of the current (scalar) and area vector at that point. The $\sigma$ is the conductivity of the conductor.
The electric field and magnetic field can be thought of as two faces of the same coin, one generate the other and vice versa.
Kshitij Kumar
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There is an electric field in the circuit that pushes the charges, and it is created by something called surface charges. If you want to read up more about it, I recommend that you look at Chapter 18 in this book called Matter and Interactions by Bruce Sherwood.
Luo Zeyuan
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Yes, there should be an electric field.
As we know the following relation holds
$$\vec{J}= \sigma \vec{E}$$
So now if there is current in the circuit there also must be an Electric field.
Now that was a bit obvious as a potential difference between two points in the wire would arise because of an electric field only.
