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Question:
A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire?
Answer:

Current in the wire, I = 35 A

Distance of a point from the wire, r = 20 cm = 0.2 m

Magnitude of the magnetic field at this point is given as:

Bimage007 NCERT Solutions class-12 physics Moving Charges and Magnetismimage008 NCERT Solutions class-12 physics Moving Charges and Magnetism

Where,

image004 NCERT Solutions class-12 physics Moving Charges and Magnetism = Permeability of free space = image009 NCERT Solutions class-12 physics Moving Charges and Magnetism

image010 NCERT Solutions class-12 physics Moving Charges and Magnetism

image011 NCERT Solutions class-12 physics Moving Charges and Magnetism

Hence, the magnitude of the magnetic field at a point 20 cm from the wire is image003 NCERT Solutions class-12 physics Moving Charges and Magnetism

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