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Question:
Two concentric circular coils X and Y of radii 16 cm and 10 cm, respectively, lie in the same vertical plane containing the north to south direction. Coil X has 20 turns and carries a current of 16 A; coil Y has 25 turns and carries a current of 18 A. The sense of the current in X is anticlockwise, and clockwise in Y, for an observer looking at the coils facing west. Give the magnitude and direction of the net magnetic field due to the coils at their centre.
Answer:

Radius of coil X, r1 = 16 cm = 0.16 m

Radius of coil Y, r2 = 10 cm = 0.1 m

Number of turns of on coil X, n1 = 20

Number of turns of on coil Y, n2 = 25

Current in coil X, I1 = 16 A

Current in coil Y, I2 = 18 A

Magnetic field due to coil X at their centre is given by the relation,

image061 NCERT Solutions class-12 physics Moving Charges and Magnetism

Where,

image004 NCERT Solutions class-12 physics Moving Charges and Magnetism = Permeability of free space = image014 NCERT Solutions class-12 physics Moving Charges and Magnetism

image062 NCERT Solutions class-12 physics Moving Charges and Magnetism

image063 NCERT Solutions class-12 physics Moving Charges and Magnetism(towards East)

Magnetic field due to coil Y at their centre is given by the relation, image064 NCERT Solutions class-12 physics Moving Charges and Magnetism

image065 NCERT Solutions class-12 physics Moving Charges and Magnetism

image066 NCERT Solutions class-12 physics Moving Charges and Magnetism(towards East)

Hence, net magnetic field can be obtained as:

image067 NCERT Solutions class-12 physics Moving Charges and Magnetism

image068 NCERT Solutions class-12 physics Moving Charges and Magnetism

image069 NCERT Solutions class-12 physics Moving Charges and Magnetism

image070 NCERT Solutions class-12 physics Moving Charges and Magnetism

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