Electrical – Voltage between two wires

voltage

In my textbook we are given the question below. I understand how to get the answer of B. But I am confused as to why the answer of A is 10 volts where the difference is 20 volts.. 10 and -10? Where is my logic or understanding wrong?

In your circuit, two wires connected to a 10-V voltage supply happen to be very close to each other at a certain location; they are separated by 2 mm.

  • A. What is the voltage between the wires at this location?

Wouldn't the difference be 20 V? But the answer key says 10 V, why is
this?

  • B. What is approximately the electric field strength at this
    location?

(Answer A) / .002 = ..

Best Answer

Two wires connected to a voltage source of 10V (the polarity is of no importance here) have the same voltage over the whole length under the following conditions.

  1. There is no flow of current (Not mentioned in the question).

Think also of this.

If there was a current you would need also the resistance of the wire expressed in Ohm/m and the distance of the 2 mm spot from the source.

  1. They do not touch each other (2mm distance as in the question)

Remember that the expression of fieldstrengh is V/m

The field strengh depends on the voltage and distance. Therefore in the question we have 10V/2mm = 5000 V/m.

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