CBSE Class 12 Physics Magnetic Effect of Current Solved Examples.

CBSE Class 12 Physics Magnetic Effect of Current Solved Examples.. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Ex.1 For the magnetic field, due to a small element of a current carrying conductor at a point to be maximum, the angle between the element and the line joining the element to point P must be-
(A) 0º (B) 90º (C) 180º (D) 45º

Sol. (B)
dB = μ0 idlsinθ/4π²
When θ = 90º, then dB will be maximum.

Ex.2 A current of 30 A is flowing in a vertical straight wire. If the horizontal component of earth's magnetic field is 2 x 10^-5 Tesla then the position of null point will be-
(A) 0.9 m (B) 0.3 mm (C) 0.3 cm (D) 0.3 m

Ex.3 A length L of wire carrying current I is bent into a circle of one turn. The field at the center of the coil is B₁. A similar wire of length L carrying current I is bent into a square of one turn. The field at its center is B₂. Then-
(A) B₁> B₂(B)  B₁ < B₂(C)  B₁ = B₂ (D) Nothing can be predicted.

Ex.4 If a uniform wire loop is connected to the terminals of a battery then the magnetic induction at the centre will be-
(A) zero (B) infinite (C) directly proportional to applied e.m.f. (D) inversely proportional to the radius of the loop.
Sol. (A)

Ex.6 A current i is flowing in a conductor shaped as shown in the figure. The radius of curved part is r and length of straight portions is very large. The value of magnetic field at the centre will be-

Ex.7 Electric currents i1 and i2 are flowing in two mutually perpendicular conductors as shown in the figure. The equation of zero magnetic field points will be-

Ex.8 In the above problem the locus of zero magnetic field points will be-
(A) a circle (B) an ellipse (C) a straight line (D) a parabola
Sol. (C) y =i₁/i₂ x, y = mx where m = i₁/i₂
This is the equation of a straight line passing
through origin.
Ex.9 In the above problems the points of zero magnetic field are-
(A) C (B) C and D (C) D and E (D) E

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