A person holds a small compass near a long, straight wire that is carrying a cur

Question

A person holds a small compass near a long, straight wire that is carrying a current, but detects no deflection of the compass needle and therefore concludes that there is no magnetic field near the wire. Which of the following statements is most likely the assumption made by the person to arrive at this conclusion? a. The wire is carrying a current. b. Any magnetic field due to a current in a wire is much greater than the earth's magnetic field. c. The wire is at least several meters long and is insulated. d. There is no deflection of the compass needle near the wire. e. Current has been flowing through the wire for an extended period of time.

Explanation / Answer

a. the answer is less appropriate because when there is a current in wire it generates magnetic field around it.So there is possibility of deflection of compass needle.

b.Magnetic field due to a current may not be alsways greater than earths magnetic field. because the field strength depends on magnitude of current.Again what ever be the field compass will deflect.So this is inappropriate.

c.Insulation of conductor does not affect magnetic field.insulated conductor carrying current generates magnetic field.So this is in appropriate.

d.This is the most approproate assumption.Because by Biot savarts law a current carrying conductor generates cmagnetic field around itself.But there is no magnetic field at a point along the length.so if a compass is held near the conductor along its length it may not show deflection.

e.Current always generates magnetic field independent of time.so this is inappropriate.

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