Q. 6

In a coaxial, straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero
A. outside the cable

B. inside the inner conductor

C. inside the outer conductor

D. in between the two conductors

Class 12th HC Verma - Concepts of Physics Part 2 35. Magnetic Field due to a Current

Answer :

According to Ampere’s Law:
Where,

B is the magnetic field,

dl is the current element,

μ₀ is the permeability of free space

i is the current flowing in the conductor

Magnetic field outside the cable: B = B_I+B_OB_I and B_O are the magnetic field of the inner conductor and outer cable respectively.
Due to wire,
R is the radius of the wire.

Thus, option (A) is the correct option.

Magnetic field inside the inner conductor:

∮B. dl =μ_o I (I=0(inside the wire))

Magnetic field between the two conductors and inside the outer conductor.

∮B. dl =μ_o I

On integrating the length element over the complete loop, we get dl= 2π r

B.2π r=μ_o I

On solving the above equation for B, we get

Thus, option A and B is the correct option.

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PREVIOUSA hollow tube is carrying an electric current along its length distributed uniformly over its surface. The magnetic field.NEXTA steady electric current is flowing through a cylindrical conductor.

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