Question

A straight wire, labeled as Wire A, lies horizontally on a tabletop and is oriented to run north-south. A conventional current of 1.0 amperes runs in the wire directed towards the north. A second wire, labeled as Wire B, is also laid on the tabletop oriented north-south. Which of the following statements is true?
(i) If Wire B carries no current in it and lies to the left (west) of wire A, then it will experience an attractive force to the right (towards wire A).
(ii) If Wire B carries a northward conventional current and lies to the left (west) of wire A, then it will experience an attractive force to the right (towards Wire A).
(iii) If Wire B carries a northward conventional current and lies to the right (east) of wire A, then it will experience a repulsive force to the right (away from Wire A).
(iv) If Wire B carries a southward conventional current and lies to the left (west) of wire A, then it will experience a repulsive force to the left (away from Wire A).
Select the correct answer:
a. Only statements (i), (ii) and (iii) are true.
b. Only statements (i) and (iii) are true.
c. Only statements (ii), (iii), and (iv) are true.
d. Only statements (ii) and (iv) are true.
e. All statements are true
f. None of the statements are true.

Answer 1

Answer:

d. Only statements (ii) and (iv) are true.

Explanation:

When current flows through a conductor (e.g wire), magnetic field is induced around the wire. The direction of the field could be determined by either the clenched fist rule or cork screw rule.

When two straight wires carries current in the same direction, there would be a force of attraction because of the re-alignment of the induced magnetism on them. But when the current flows in opposite directions, repulsion is observed.