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Question
Choose the correct option:
Figures (a) and (b) show two Amperean loops associated with the conductors carrying current I in the sense shown. The `oint vecB * vecdl` in the cases (a) and (b) are, respectively.
Options
– µ0I, 0
µ0I, 0
0, µ0I
0, – µ0I
Solution
– µ0I, 0
Explanation:
Express the relation of Ampere’s law.
`oint B * ds = mu_0 I`
The figure below shows the direction of the magnetic field by right-hand thumb rule.
Here, fingers represent the direction of the magnetic field and thumb represents the direction of the current.
Apply right-hand thumb rule in both cases.
Part I
As the direction of the magnetic field is in an anticlockwise direction. By applying right-hand thumb rule, the direction of current should be from right to left (according to this figure). But the direction of the current is opposite.
Part II
The right-hand thumb rule is only applicable in a closed loop.
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