Magnetic Effect of Current
240 Questions
Start JEE Mains Test
2018
Q201
JEE Mains
MCQ
10 Mar 2026
A current of 1 A is flowing on the sides of an equilateral triangle of side 4.5 $ \times $ 10-2 m. The magnetic field at the center of the triangle will be :
A.
2 $ \times $ 10-5 Wb/m2
B.
Zero
C.
8 $ \times $ 10-5 Wb/m2
D.
4 $ \times $ 10-5 Wb/m2
2018
Q202
JEE Mains
MCQ
10 Mar 2026
A Helmholtz coil has a pair of loops, each with $N$ turns and radius $R$. They are placed coaxially at distance $R$ and the same current ${\rm I}$ flows through the loops in the same direction. $P,$ midway between the centers $A$ and $C$, is given by [Refer to figure given below] :
A.
${{8N{\mu _0}{\rm I}} \over {{5^{1/2}}R}}$
B.
${{8N{\mu _0}{\rm I}} \over {{5^{3/2}}R}}$
C.
${{4N{\mu _0}{\rm I}} \over {{5^{1/2}}R}}$
D.
${{4N{\mu _0}{\rm I}} \over {{5^{3/2}}R}}$
2017
Q203
JEE Mains
MCQ
10 Mar 2026
A negative test charge is moving near a long straight wire carrying a current. The force acting on the test charge is parallel to the direction of the current. The motion of the charge is :
A.
away from the wire
B.
towards the wire
C.
parallel to the wire along the current
D.
parallel to the wire opposite to the current
2017
Q204
JEE Mains
MCQ
10 Mar 2026
In a certain region static electric and magnetic fields exist. The magnetic field is given by $\overrightarrow B = {B_0}\left( {\widehat i + 2\widehat j - 4\widehat k} \right)$ . If a test charge moving with a velocity $\overrightarrow \upsilon = {\upsilon _0}\left( {3\widehat i - \widehat j + 2\widehat k} \right)$ experiences no force in that region, then the electric field in the region, in SI units, is :
A.
$\overrightarrow E = - {\upsilon _0}\,{B_0}\left( {3\widehat i - 2\widehat j - 4\widehat k} \right)$
B.
$\overrightarrow E = - {\upsilon _0}\,{B_0}\left( {\widehat i + \widehat j + 7\widehat k} \right)$
C.
$\overrightarrow E = {\upsilon _0}\,{B_0}\left( {14\widehat j + 7\widehat k} \right)$
D.
$\overrightarrow E = - {\upsilon _0}\,{B_0}\left( {14\widehat j + 7\widehat k} \right)$
2017
Q205
JEE Mains
MCQ
10 Mar 2026
A magnetic dipole in a constant magnetic field has :
A.
maximum potential energy when the torque is maximum.
B.
zero potential energy when the torque is minimum.
C.
zero potential energy when the torque is maximum.
D.
minimum potential energy when the torque is maximum.
2016
Q206
JEE Mains
MCQ
10 Mar 2026
A magnetic dipole is acted upon by two magnetic fields which are inclined to each other at an angle of 75o. One of the fields has a magnitude of 15 mT. The dipole attains stable equilibrium at an angle of 30o with this field. The magnitude of the other field (in mT ) is close to
A.
11
B.
36
C.
1
D.
1060
2016
Q207
JEE Mains
MCQ
10 Mar 2026
To know the resistance G of a galvanometer by half deflection method, a battery of emf VE and resistance R is used to deflect the galvanometer by angle $\theta $. If a shunt of resistance S is needed to get half deflection then G, R and S are related by the equation :
A.
2S (R + G) = RG
B.
S (R + G) = RG
C.
2S = G
D.
2G = S
2016
Q208
JEE Mains
MCQ
10 Mar 2026
Two identical wires $A$ and $B,$ each of length $'l'$, carry the same current $I$. Wire $A$ is bent into a circle of radius $R$ and wire $B$ is bent to form a square of side $'a'$. If ${B_A}$ and ${B_B}$ are the values of magnetic fields at the centres of the circle and square respectively, then the ratio ${{{B_A}} \over {{B_B}}}$ is:
A.
${{{\pi ^2}} \over {16}}$
B.
${{{\pi ^2}} \over {8\sqrt 2 }}$
C.
${{{\pi ^2}} \over {8}}$
D.
${{{\pi ^2}} \over {16\sqrt 2 }}$
2015
Q209
JEE Mains
MCQ
10 Mar 2026
Two long current carrying thin wires, both with current $I,$ are held by insulating threads of length $L$ and are in equilibrium as shown in the figure, with threads making an angle $'\theta '$ with the vertical. If wires have mass $\lambda $ per unit-length then the value of $I$ is :
($g=$ $gravitational$ $acceleration$ )
($g=$ $gravitational$ $acceleration$ )
A.
$2\sqrt {{{\pi gL} \over {{\mu _0}}}\tan \theta } $
B.
$\sqrt {{{\pi \lambda gL} \over {{\mu _0}}}\tan \theta } $
C.
$\sin \theta \sqrt {{{\pi \lambda gL} \over {{\mu _0}\,\cos \theta }}} $
D.
$2\sin \theta \sqrt {{{\pi \lambda gL} \over {{\mu _0}\,\cos \theta }}} $
2015
Q210
JEE Mains
MCQ
10 Mar 2026
A rectangular loop of sides $10$ $cm$ and $5$ $cm$ carrying a current $1$ of $12A$ is placed in different orientations as shown in the figures below :
If there is a uniform magnetic field of $0.3$ $T$ in the positive $z$ direction, in which orientations the loop would be in $(i)$ stable equilibrium and $(ii)$ unstable equilibrium ?
A.
$(B)$ and $(D)$, respectively
B.
$(B)$ and $(C)$, respectively
C.
$(A)$ and $(B)$, respectively
D.
$(A)$ and $(C)$, respectively
2014
Q211
JEE Mains
MCQ
10 Mar 2026
A conductor lies along the $z$-axis at $ - 1.5 \le z < 1.5\,m$ and carries a fixed current of $10.0$ $A$ in $ - {\widehat a_z}$ direction (see figure). For a field $\overrightarrow B = 3.0 \times {10^{ - 4}}\,{e^{ - 0.2x}}\,\,{\widehat a_y}\,\,T,$ find the power required to move the conductor at constant speed to $x=2.0$ $m$, $y=0$ $m$ in $5 \times {10^{ - 3}}s.$ Assume parallel motion along the $x$-axis.
A.
$1.57W$
B.
$2.97W$
C.
$14.85$ $W$
D.
$29.7W$
2012
Q212
JEE Mains
MCQ
10 Mar 2026
A charge $Q$ is uniformly distributed over the surface of non-conducting disc of radius $R.$ The disc rotates about an axis perpendicular to its plane and passing through its center with an angular velocity $\omega .$ As a result of this rotation a magnetic field of induction $B$ is obtained at the center of the disc. If we keep both the amount of charge placed on the disc and its angular velocity to be constant and very the radius of the disc then the variation of the magnetic induction at the center of the disc will be represented by the figure :
A.
B.
C.
D.
2012
Q213
JEE Mains
MCQ
10 Mar 2026
Proton, deuteron and alpha particle of same kinetic energy are moving in circular trajectories in a constant magnetic field. The radii of proton, denuteron and alpha particle are respectively ${r_p},{r_d}$ and ${r_\alpha }$. Which one of the following relation is correct?
A.
${r_\alpha } = {r_p} = {r_d}$
B.
${r_\alpha } = {r_p} < {r_d}$
C.
${r_\alpha } > {r_d} > {r_p}$
D.
${r_\alpha } = {r_d} > {r_p}$
2011
Q214
JEE Mains
MCQ
10 Mar 2026
A current $I$ flows in an infinitely long wire with cross section in the form of a semi-circular ring of radius $R.$ The magnitude of the magnetic induction along its axis is:
A.
${{{\mu _0}I} \over {2{\pi ^2}R}}$
B.
${{{\mu _0}I} \over {2\pi R}}$
C.
${{{\mu _0}I} \over {4\pi R}}$
D.
${{{\mu _0}I} \over {{\pi ^2}R}}$
2010
Q215
JEE Mains
MCQ
10 Mar 2026
Two long parallel wires are at a distance $2d$ apart. They carry steady equal currents flowing out of the plane of the paper as shown. The variation of the magnetic field $B$ along the line $XX'$ is given by
A.
B.
C.
D.
2009
Q216
JEE Mains
MCQ
10 Mar 2026
A current loop $ABCD$ is held fixed on the plane of the paper as shown in the figure. The arcs $BC$ (radius $= b$) and $DA$ (radius $=a$) of the loop are joined by two straight wires $AB$ and $CD$. A steady current $I$ is flowing in the loop. Angle made by $AB$ and $CD$ at the origin $O$ is ${30^ \circ }.$ Another straight thin wire steady current ${I_1}$ flowing out of the plane of the paper is kept at the origin.
Due to the presence of the current ${I_1}$ at the origin:
A.
The forces on $AD$ are $BC$ are zero.
B.
The magnitude of the net force on the loop is given by ${{{I_1}I} \over {4\pi }}{\mu _0}\left[ {2\left( {b - a} \right) + {\raise0.5ex\hbox{$\scriptstyle \pi $}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle 3$}}\left( {a + b} \right)} \right].$
C.
The magnitude of the net force on the loop is given by ${{{\mu _0}I{I_1}} \over {24ab}}\left( {b - a} \right).$
D.
The forces on $AB$ and $DC$ are zero.
2009
Q217
JEE Mains
MCQ
10 Mar 2026
A current loop $ABCD$ is held fixed on the plane of the paper as shown in the figure. The arcs $BC$ (radius $= b$) and $DA$ (radius $=a$) of the loop are joined by two straight wires $AB$ and $CD$. A steady current $I$ is flowing in the loop. Angle made by $AB$ and $CD$ at the origin $O$ is ${30^ \circ }.$ Another straight thin wire steady current ${I_1}$ flowing out of the plane of the paper is kept at the origin.
The magnitude of the magnetic field $(B)$ due to the loop $ABCD$ at the origin $(O)$ is :
A.
${{{\mu _0}I\left( {b - a} \right)} \over {24ab}}$
B.
${{{\mu _0}I} \over {4\pi }}\left[ {{{b - a} \over {ab}}} \right]$
C.
${{{\mu _0}I} \over {4\pi }}\left[ {2\left( {b - a} \right) + {\raise0.5ex\hbox{$\scriptstyle \pi $}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle 3$}}\left( {a + b} \right)} \right]$
D.
zero
2008
Q218
JEE Mains
MCQ
10 Mar 2026
A horizontal overhead powerline is at height of $4m$ from the ground and carries a current of $100A$ from east to west. The magnetic field directly below it on the ground is
$\left( {{\mu _0} = 4\pi \times {{10}^{ - 7}}\,\,Tm\,\,{A^{ - 1}}} \right)$
$\left( {{\mu _0} = 4\pi \times {{10}^{ - 7}}\,\,Tm\,\,{A^{ - 1}}} \right)$
A.
$2.5 \times {10^{ - 7}}\,T$ southward
B.
$5 \times {10^{ - 6}}\,T$ northward
C.
$5 \times {10^{ - 6}}\,T$ southward
D.
$2.5 \times {10^{ - 7}}\,T$ northward
2007
Q219
JEE Mains
MCQ
10 Mar 2026
A charged particle with charge $q$ enters a region of constant, uniform and mutually orthogonal fields $\overrightarrow E $ and $\overrightarrow B $ with a velocity $\overrightarrow v $ perpendicular to both $\overrightarrow E $ and $\overrightarrow B, $ and comes out without any change in magnitude or direction of $\overrightarrow v $. Then
A.
$\overrightarrow v = \overrightarrow B \times \overrightarrow E /{E^2}$
B.
$\overrightarrow v = \overrightarrow E \times \overrightarrow B /{B^2}$
C.
$\overrightarrow v = \overrightarrow B \times \overrightarrow E /{B^2}$
D.
$\overrightarrow v = \overrightarrow E \times \overrightarrow B /{E^2}$
2007
Q220
JEE Mains
MCQ
10 Mar 2026
Two identical conducting wires $AOB$ and $COD$ are placed at right angles to each other. The wire $AOB$ carries an electric current ${I_1}$ and $COD$ carries a current ${I_2}$. The magnetic field on a point lying at a distance $d$ from $O$, in a direction perpendicular to the plane of the wires $AOB$ and $COD$ , will be given by
A.
${{{\mu _0}} \over {2\pi d}}\left( {I_1^2 + I_2^2} \right)$
B.
${{{\mu _0}} \over {2\pi }}{\left( {{{{I_1} + {I_2}} \over d}} \right)^{{1 \over 2}}}$
C.
${{{\mu _0}} \over {2\pi d}}{\left( {I_1^2 + I_2^2} \right)^{{1 \over 2}}}$
D.
${{{\mu _0}} \over {2\pi d}}\left( {{I_1} + {I_2}} \right)$
2007
Q221
JEE Mains
MCQ
10 Mar 2026
A charged particle moves through a magnetic field perpendicular to its direction. Then
A.
Kinetic energy changes but the momentum is constant
B.
the momentum changes but the kinetic energy is constant
C.
both momentum and kinetic energy of the particle are not constant
D.
both momentum and kinetic energy of the particle are constant
2007
Q222
JEE Mains
MCQ
10 Mar 2026
A long straight wire of radius $a$ carries a steady current $i.$ The current is uniformly distributed across its cross section. The ratio of the magnetic field at $a/2$ and $2a$ is
A.
$1/2$
B.
$1/4$
C.
$4$
D.
$1$
2007
Q223
JEE Mains
MCQ
10 Mar 2026
A current $I$ flows along the length of an infinitely long, straight, thin walled pipe. Then
A.
the magnetic field at all points inside the pipe is the same, but not zero
B.
the magnetic field is zero only on the axis of the pipe
C.
the magnetic field is different at different points inside the pipe
D.
the magnetic field at any point inside the pipe is zero
2006
Q224
JEE Mains
MCQ
10 Mar 2026
In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a
A.
helix
B.
straight line
C.
ellipse
D.
circle
2006
Q225
JEE Mains
MCQ
10 Mar 2026
A long solenoid has $200$ turns per $cm$ and carries a current $i.$ The magnetic field at its center is $6.28 \times {10^{ - 2}}\,\,\,Weber/{m^2}.$ Another long solenoid has $100$ turns per $cm$ and it carries a current ${i \over 3}$. The value of the magnetic field at its center is
A.
$1.05 \times {10^{ - 2}}\,\,Weber/{m^2}$
B.
$1.05 \times {10^{ - 5}}\,\,Weber/{m^2}$
C.
$1.05 \times {10^{ - 3}}\,\,Weber/{m^2}$
D.
$1.05 \times {10^{ - 4}}\,\,Weber/{m^2}$
2005
Q226
JEE Mains
MCQ
10 Mar 2026
A charged particle of mass $m$ and charge $q$ travels on a circular path of radius $r$ that is perpendicular to a magnetic field $B.$ The time taken by the particle to complete one revolution is
A.
${{2\pi {q^2}B} \over m}$
B.
${{2\pi mq} \over B}$
C.
${{2\pi m} \over {qB}}$
D.
${{2\pi qB} \over m}$
2005
Q227
JEE Mains
MCQ
10 Mar 2026
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity then
A.
its velocity will increase
B.
Its velocity will decrease
C.
it will turn towards left of a direction of motion
D.
it will turn towards right of direction of motion
2005
Q228
JEE Mains
MCQ
10 Mar 2026
Two thin, long, parallel wires, separated by a distance $'d'$ carry a current of $'i'$ $A$ in the same direction. They will
A.
repel each other with a force of ${\mu _0}{i^2}/\left( {2\pi d} \right)$
B.
attract each other with a force of ${\mu _0}{i^2}/\left( {2\pi d} \right)$
C.
repel each other with a force $_0{i^2}/\left( {2\pi {d^2}} \right)$
D.
attract each other with a force of ${\mu _0}{i^2}/\left( {2\pi {d^2}} \right)$
2005
Q229
JEE Mains
MCQ
10 Mar 2026
Two concentric coils each of radius equal to $2$ $\pi $ $cm$ are placed at right angles to each other. $3$ ampere and $4$ ampere are the currents flowing in each coil respectively . The magnetic induction in Weber / ${m^2}$ at the center of the coils will be
$\left( {\mu = 4\pi \times {{10}^{ - 7}}Wb/A.m} \right)$
$\left( {\mu = 4\pi \times {{10}^{ - 7}}Wb/A.m} \right)$
A.
${10^{ - 5}}$
B.
$12 \times {10^{ - 5}}$
C.
$7 \times {10^{ - 5}}$
D.
$5 \times {10^{ - 5}}$
2004
Q230
JEE Mains
MCQ
10 Mar 2026
The magnetic field due to a current carrying circular loop of radius $3$ $cm$ at a point on the axis at a distance of $4$ $cm$ from the centre is $54\,\mu T.$ What will be its value at the center of loop?
A.
$125\,\mu T$
B.
$150\,\mu T$
C.
$250\,\mu T$
D.
$75\,\mu T$
2004
Q231
JEE Mains
MCQ
10 Mar 2026
A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is $B.$ It is then bent into a circular loop of $n$ turns. The magnetic field at the center of the coil will be
A.
$2n$ $B$
B.
${n^2}\,B$
C.
$nB$
D.
$2{n^2}\,B$
2004
Q232
JEE Mains
MCQ
10 Mar 2026
Two long conductors, separated by a distance $d$ carry current ${I_1}$ and ${I_2}$ in the same direction. They exert a force $F$ on each other. Now the current in one of them is increased to two times and its direction is reversed. The distance is also increased to $3d$. The new value of the force between them is
A.
$ - {{2F} \over 3}$
B.
${F \over 3}$
C.
$-2F$
D.
$ - {F \over 3}$
2004
Q233
JEE Mains
MCQ
10 Mar 2026
A current $i$ ampere flows along an infinitely long straight thin walled tube, then the magnetic induction at any point inside the tube is
A.
${{{\mu _0}} \over {4\pi }},{{2i} \over r}$ tesla
B.
zero
C.
infinite
D.
${{2i} \over r}$ tesla
2003
Q234
JEE Mains
MCQ
10 Mar 2026
A particle of charge $ - 16 \times {10^{ - 18}}$ coulomb moving with velocity $10m{s^{ - 1}}$ along the $x$-axis enters a region where a magnetic field of induction $B$ is along the $y$-axis, and an electric field of magnitude ${10^4}V/m$ is along the negative $z$-axis. If the charged particle continues moving along the $x$-axis, the magnitude of $B$ is
A.
${10^3}Wb/{m^2}$
B.
${10^5}Wb/{m^2}$
C.
${10^{16}}Wb/{m^2}$
D.
${10^{ - 3}}Wb/{m^2}$
2003
Q235
JEE Mains
MCQ
10 Mar 2026
A particle of mass $M$ and charge $Q$ moving with velocity $\overrightarrow v $ describe a circular path of radius $R$ when subjected to a uniform transverse magnetic field of induction $B.$ The network done by the field when the particle completes one full circle is
A.
$\left( {{{M{v^2}} \over R}} \right)2\pi R$
B.
zero
C.
$B\,\,Q\,2\pi R$
D.
$B\,Qv\,2\pi R$
2002
Q236
JEE Mains
MCQ
10 Mar 2026
If a current is passed through a spring then the spring will
A.
expand
B.
compress
C.
remains same
D.
none of these
2002
Q237
JEE Mains
MCQ
10 Mar 2026
Wires $1$ and $2$ carrying currents $i{}_1$ and $i{}_2$ respectively are inclined at an angle $\theta $ to each other. What is the force on a small element $dl$ of wire $2$ at a distance of $r$ from wire $1$ (as shown in figure) due to the magnetic field of wire $1$?
A.
${{{\mu _0}} \over {2\pi r}}{i_1}{i_2}\,dl\,\tan \,\theta $
B.
${{{\mu _0}} \over {2\pi r}}{i_1}{i_2}\,dl\,\sin \,\theta $
C.
${{{\mu _0}} \over {2\pi r}}{i_1}{i_2}\,dl\,\cos \,\theta $
D.
${{{\mu _0}} \over {4\pi r}}{i_1}{i_2}\,dl\,\sin \,\theta $
2002
Q238
JEE Mains
MCQ
10 Mar 2026
If an electron and a proton having same momentum enter perpendicular to a magnetic field, then
A.
curved path of electron and proton will be same (ignoring the sense of revolution)
B.
they will move undeflected
C.
curved path of electron is more curved than that of the proton
D.
path of proton is more curved.
2002
Q239
JEE Mains
MCQ
10 Mar 2026
If in a circular coil $A$ of radius $R,$ current $I$ is flowing and in another coil $B$ of radius $2R$ a current $2I$ is flowing, then the ratio of the magnetic fields ${B_A}$ and ${B_B}$, produced by them will be
A.
$1$
B.
$2$
C.
$1/2$
D.
$4$
2002
Q240
JEE Mains
MCQ
10 Mar 2026
The time period of a charged particle undergoing a circular motion in a uniform magnetic field is independent of its
A.
speed
B.
mass
C.
charge
D.
magnetic induction