Source And Effects Of Magnetic Field | Physics JEE previous year questions with Solutions

Q 11 :

As shown in the figure, a current of 2 A flowing in an equilateral triangle of side $4 \sqrt{3}$ cm. The magnetic field at the centroid $O$ of the triangle is [2023]

(Neglect the effect of earth's magnetic field.)

$4 \sqrt{3} \times 10^{- 4} T$
$4 \sqrt{3} \times 10^{- 5} T$
$\sqrt{3} \times 10^{- 4} T$
$3 \sqrt{3} \times 10^{- 5} T$

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(4)

$d \tan 60 ° = 2 \sqrt{3}$

$d = 2 cm$

$B = 3 \times \frac{μ_{0} i}{2 π d} \sin 60 °$

$= 3 \times \frac{2 \times 10^{- 7} \times 2}{2 \times 10^{- 2}} \times \frac{\sqrt{3}}{2}$

$= 3 \sqrt{3} \times 10^{- 5}$

Q 12 :

Two long parallel wires carrying currents 8 A and 15 A in opposite directions are placed at a distance of 7 cm from each other. A point $P$ is at equidistant from both the wires such that the lines joining the point $P$ to the wires are perpendicular to each other. The magnitude of magnetic field at $P$ is ________ $\times 10^{- 6} T$ . (Given: $\sqrt{2} = 1.4$ ) [2023]

0%

(68)

$Magnetic fields due to both wires will be perpendicular to each other.$

$B_{1} = \frac{μ_{0} i_{1}}{2 π d}, B_{2} = \frac{μ_{0} i_{2}}{2 π d}$

$B_{net} = \sqrt{B_{1}^{2} + B_{2}^{2}} = \frac{μ_{0}}{2 π d} \sqrt{i_{1}^{2} + i_{2}^{2}}$

$\Rightarrow \frac{4 π \times 10^{- 7}}{2 π \times (\frac{7}{\sqrt{2}}) \times 10^{- 2}} \times \sqrt{8^{2} + 15^{2}} (d = \frac{7}{\sqrt{2}} cm)$

$= 68 \times 10^{- 6} T$

Q 13 :

An electron in a hydrogen atom revolves around its nucleus with a speed of $6.76 \times 10^{6} {ms}^{- 1}$ in an orbit of radius $0.52 Å$ . The magnetic field produced at the nucleus of the hydrogen atom is _________ T. [2023]

0%

(40)

$Magnetic field due to moving charge$

$B = \frac{μ_{0}}{4 π} \frac{q v \sin θ}{r^{2}}$

$B = \frac{μ_{0}}{4 π} \frac{e v \sin (π / 2)}{r^{2}}$

$B = \frac{10^{- 7} \times 1.6 \times 10^{- 19} \times 6.76 \times 10^{6}}{0.52 \times 0.52 \times 10^{- 20}}$

$\Rightarrow B = 40 T$

Q 14 :

A long cylindrical conductor with large cross section carries an electric current distributed uniformly over its cross-section. Magnetic field due to this current is :

A. maximum at either ends of the conductor and minimum at the midpoint
B. maximum at the axis of the conductor
C. minimum at the surface of the conductor
D. minimum at the axis of the conductor
E. same at all points in the cross-section of the conductor

Choose the correct answer from the options given below : [2026]

B, C Only
D Only
A, D Only
E Only

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(2)

Q 15 :

The current passing through a conducting loop in the form of equilateral triangle of side $4 \sqrt{3} cm$ is 2 A. The magnetic field at its centroid is $α \times 10^{- 5} T$ The value of $α$ is ______.

$(G i v e n : μ_{0} = 4 π \times 10^{- 7} S I u n i t s)$ [2026]

$\frac{\sqrt{3}}{2}$
$\sqrt{3}$
$3 \sqrt{3}$
$2 \sqrt{3}$

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(3)

Topic Question Set

Q 11 :

As shown in the figure, a current of 2 A flowing in an equilateral triangle of side $4 \sqrt{3}$ cm. The magnetic field at the centroid $O$ of the triangle is [2023]

(Neglect the effect of earth's magnetic field.)

0%

Q 13 :

An electron in a hydrogen atom revolves around its nucleus with a speed of $6.76 \times 10^{6} {ms}^{- 1}$ in an orbit of radius $0.52 Å$ . The magnetic field produced at the nucleus of the hydrogen atom is _________ T. [2023]

0%

Q 15 :

The current passing through a conducting loop in the form of equilateral triangle of side $4 \sqrt{3} cm$ is 2 A. The magnetic field at its centroid is $α \times 10^{- 5} T$ The value of $α$ is ______.

$(G i v e n : μ_{0} = 4 π \times 10^{- 7} S I u n i t s)$ [2026]

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