Magnetic field lines, generated by a long straight wire carrying a current, are circles concentric with the wire and lie in planes perpendicular to the wire.
a. true
b. false

True

Explanation:

It is true that magnetic field lines around a current carrying wire is in the form of concentric circles and lie in the plane perpendicular to the wire.

This Fact can be Proven by placing the iron filling around the wire and they will be arranged like concentric circles and Magnetic field intensity diminishes as we go away from the wire.  

as we probably am aware that our atmosphere or air have various levels, each level has different gasses, and each gas has another porousness. at the point when the light originates from lower porousness to higher penetrability, it alters its course. with the goal that implies that when the light originates from the moon to the earth, it alters it's course a lot more occasions. it essentially implies that the state of the light piece of the moon is changed on the earth.

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joke:

h o h o hope you have a merry christmas!