# Electric field of a conductor

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1. Aug 22, 2015

### gruba

1. The problem statement, all variables and given/known data
Wire conductor of length l consists of two part with equal length in series, and of specific conductivity σ1 and σ2. When conductor is connected to constant voltage U, what are electric fields in parts of this conductor?

2. Relevant equations
$$J=σE$$

3. The attempt at a solution
Electric fields should be $$E_1=\frac{2σ_2U}{l(σ_1+σ_2)}$$
$$E_2=\frac{2σ_1U}{l(σ_1+σ_2)}$$
I don't know how to derive these equations.
Could someone give a hint?

Thanks for replies.

2. Aug 22, 2015

### Staff: Mentor

What do you know about the current flow per area?
You can introduce a cross-section A if that helps (that allows to calculate the total resistance and total current flow, the area will drop out later).