Two long straight wires are suspended vertically

Question

The wires are connected in series, and a current from a battery is maintained in them. What happens to the wires? What happens if the battery is replaced by an a-c source?

Answer 1

The wires will be attracted to each other with DC (battery).    When the A-C is turned on the wires will be attracted then continuously drop to 0 in attraction strength and then contiguously increase back up to where is was before and then continuously decrease to 0.  This cycle will repeat.

If  you want to understand why read below, otherwise above is enough:

Think of one wire alone...in an EXTERNAL magnetic field (You dont care where the field comes from or how it arises).  You must ignore the fact that the current moving in this wire creates its own magnetic field...otherwise the problem becomes confusing.    Now do the good ol right hand rule.....you have an external field, a direction of current and a force that the wire will feel  (dont get the force that it feels mixed up with the force that it can exert.  At the moment it is not exerting any force..it only feels a force).     Put your hand like you are doing a karate chop.   stick your thumb straight to the ceiling.  The direction that your palm is facing is the direction of the magnetic field.  The thumb is current and your fingers is the force that it will feel.      Now, back to your original question.  The key to understanding is to realize that the external magnetic field on one wire is there..but this time you know that the source  is from the other wire.  Hope that helps.  Im typing too much i think

Answer 2

If the wires are in series, the currents in the wires are in opposite directions and the wires will be repeleld by one another by their magnetic fields.

With AC, same result as the instantaneous currents are always equal and opposite.

Answer 3

Wires are drawn to each other due to a magnetic field generated by the electrical current. Nothing happens.