Help With Electrostatics?? Physics Question!!?

Question

Nerve cells work by pumping sodium ions (Na+) out of the cell in order to maintain a potential difference across the cell wall. If Na+ carries a charge of 1.6×10-19 C as it is pumped with an electric force of 4.26×10-16 N, what is the electric field strength between the inside and outside of the cell?

I know you can use Coulomb's Law, but I don't know how to proceed because there doesn't seem to be enough information. How do you do this problem?

Answer 1

If the cell is a hollow conducting sphere the potential inside the sphere is 0. The electric filed is also 0 because in any point inside the sphere the field is created by all the ions on the surface of the sphere. Assuming they are all equally distributed on the surface of the sphere the resultant of the forces created by each of the ions in any point inside of the sphere is 0(because of simetry).

Answer 2

Coulombs law describes the electric field surrounding a point charge. That's not what you are looking for. You are looking for force exerted on a charge while in the presence of an external electric field. For that, you can probably just use the equation of what an electric field is. An electric field exerts force on a charge, where the force exerted is proportional to field strength and magnitude of charge.

In this case, I assume the question means that 4.26x10-16N is required to over come the electric field and to send it moving across the membrane.

So then you have F=q*E where F=force, q=charge and E=field strength. You know force required to counter the electric field and the charge on the ion. Solve for electric field strength.