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Magnetic Effect Of Current And Magnetism

189 Questions MCQ (Single Correct) Start Allen Test
All Exams Allen
Q1 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A stationary magnet does not interact with :
A.
iron rod
B.
moving charge
C.
moving magnet
D.
stationary charge
Q2 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Figure shows a square shape loop, whose one arm BC produces magnetic field B at the centre of coil. The resultant magnetic field due to all the arms will be :-
A.
4B
B.
B/2
C.
B
D.
2B
Q3 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A wire is parallel to one arm of a square current carrying loop, which also carries current. Now at any point A within the coil the magnetic field will be :-
A.
less than the magnetic field produced due to loop only.
B.
more than the magnetic field produced due to loop only.
C.
equal to the earlier.
D.
zero
Q4 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A current of 10 A is established in a long wire along positive z-direction. The magnetic field B at the point (1m, 0, 0) is:
A.
$1\mu \mathrm{T}$ along the -y direction
B.
$2\mu \mathrm{T}$ along the +y direction
C.
$1\mu \mathrm{T}$ along the -x direction
D.
$2\mu \mathrm{T}$ along the +x direction
Q5 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Radius of current carrying coil is 'R'. Then ratio of magnetic fields at the centre of the coil to the axial point, which is $R\sqrt{3}$ distance away from the centre of the coil:-
A.
1:1
B.
1:2
C.
1:4
D.
8:1
Q6 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A coil of one loop is made by a wire of length L and there after a coil of two loops is made by same wire. The ratio of magnetic field at the centre of coils respectively:-
A.
1:4
B.
1:1
C.
1:8
D.
4:1
Q7 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Magnetic field at point O will be :-
A.
$\frac{\mu_0\mathrm{I}}{2\mathrm{R}}\otimes$
B.
$\frac{\mu_0\mathrm{I}}{2\mathrm{R}}\odot$
C.
$\frac{\mu_0\mathrm{I}}{2\mathrm{R}}\left(1 - \frac{1}{\pi}\right)\otimes$
D.
$\frac{\mu_0\mathrm{I}}{2\mathrm{R}}\left(1 + \frac{1}{\pi}\right)\odot$
Q8 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
The vector form of Biot savart law for a current carrying element is :-
A.
$\mathrm{d}\vec{\mathrm{B}} = \frac{\mu_0}{4\pi}\frac{\mathrm{id}\ell\sin\phi}{\mathrm{r}^2}$
B.
$\mathrm{d}\vec{\mathrm{B}} = \frac{\mu_0}{4\pi}\frac{\mathrm{i}\vec{\mathrm{d}}\ell\times\hat{\mathrm{r}}}{\mathrm{r}^2}$
C.
$\mathrm{d}\vec{\mathrm{B}} = \frac{\mu_0}{4\pi}\frac{\mathrm{i}\vec{\mathrm{d}}\ell\times\hat{\mathrm{r}}}{\mathrm{r}^3}$
D.
$\mathrm{d}\vec{\mathrm{B}} = \frac{\mu_0}{4\pi}\frac{\mathrm{i}\vec{\mathrm{d}}\ell\times\vec{\mathrm{r}}}{\mathrm{r}^2}$
Q9 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A and B are two concentric circular loop carrying current $i_{1}$ and $i_{2}$ as shown in figure. If ratio of their radii is 1:2 and ratio of the flux densities at the centre O due to A and B is 1:3 then the value of $\frac{i_{1}}{i_{2}}$ will be :-
A.
$\frac{1}{2}$
B.
$\frac{1}{3}$
C.
$\frac{1}{4}$
D.
$\frac{1}{6}$
Q10 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
For the given current distribution the magnetic field at point, 'P' is :-
A.
$\frac{\mu_0}{4\pi}\odot$
B.
$\frac{\mu_0}{\pi}\otimes$
C.
$\frac{\mu_0}{2\pi}\otimes$
D.
$\frac{\mu_0}{2\pi}\odot$
Q11 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
1A current flows through an infinitely long straight wire. The magnetic field produced at a point 1m. away from it is:-
A.
$2 \times 10^{-3} \mathrm{T}$
B.
$\frac{2}{10} \mathrm{T}$
C.
$2 \times 10^{-7} \mathrm{T}$
D.
$2 \pi \times 10^{-6} \mathrm{T}$
Q12 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Two infinite long parallel wires carry equal currents in same direction. The magnetic field at mid point between the two wires is:-
A.
Twice the magnetic field produced due to each of the wires
B.
Half of the magnetic field produced due to each of the wires
C.
Square of the magnetic field produced due to each of the wires
D.
Zero
Q13 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A closely wound flat circular coil of 25 turns of wire has diameter of 10 cm and carries a current of 4 ampere. Determine the magnetic flux density at the centre of the coil:-
A.
$1.679 \times 10^{-5} \mathrm{T}$
B.
$2.028 \times 10^{-4} \mathrm{T}$
C.
$1.257 \times 10^{-3} \mathrm{T}$
D.
$1.512 \times 10^{-6} \mathrm{T}$
Q14 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
$\pi$ ampere current is flowing through a long straight wire. Due to this a field of $5 \times 10^{-5}$ T produced, then distance of the point from the axis of the wire is :-
A.
$10^{4}\mu_{0}\mathrm{m}$
B.
$10^{5}\mu_{0}\mathrm{m}$
C.
$10^{6}\mu_{0}\mathrm{m}$
D.
$10^{8}\mu_{0}\mathrm{m}$
Q15 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Radius of a current carrying coil is 'R'. The ratio of magnetic field at a axial point which is R distance away from the centre of the coil to the magnetic field at the centre of the coil :-
A.
$\left(\frac{1}{2}\right)^{1/2}$
B.
$\frac{1}{2}$
C.
$\left(\frac{1}{2}\right)^{3/2}$
D.
$\frac{1}{4}$
Q16 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its centre will become :-
A.
Same
B.
Four times
C.
Half
D.
Double
Q17 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Which of the following statement is not true; magnetic field at the centre of current carrying loop :-
A.
proportional to current
B.
inversely proportional to radius
C.
proportional to number of turns
D.
none
Q18 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A circular coil of radius R carries an electric current. The magnetic field due the coil at a point on the axis of the coil located at a distance r from the center of the coil, such that r >> R varies as:
A.
1/r
B.
$1 / \mathrm{r}^{3/2}$
C.
$1 / \mathrm{r}^2$
D.
$1 / \mathrm{r}^3$
Q19 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
Two concentric circular loops of radii 0.08m and 0.1m carries current such that magnetic field at the centre is zero. If the current in the outer loop is 8A clockwise, current in the inner loop is :-
A.
6.4 A anticlockwise
B.
6.4 A clockwise
C.
8A anticlockwise
D.
3.2 A clockwise
Q20 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
In the shown figure magnetic field at point A will be :-
A.
$\frac{\mu_0\mathrm{I}}{4\pi}$
B.
$\frac{\mu_0\mathrm{I}}{4\mathrm{R}}$
C.
$\frac{\mu_0\mathrm{I}}{4\pi\mathrm{R}}$
D.
Zero
Q21 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
If radius of coil becomes two times and current becomes half then magnetic field at centre of the coil will be :-
A.
Two times
B.
Four times
C.
Half
D.
One fourth
Q22 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
2A current is flowing in a circular loop of radius $1\mathrm{m}$ . Magnitude of magnetic field at the centre of circular loop will be :-
A.
$\frac{\mu_0}{2}$
B.
$2\mu_0$
C.
$\mu_0$
D.
$\frac{\mu_0}{2\pi}$
Q23 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
A horizontal overhead powerline is at a height of 4m from the ground and carries a current of 100 A from east to west. The magnetic field directly below it on the ground is :-
A.
$2.5 \times 10^{-7}\mathrm{T}$ , southward
B.
$5 \times 10^{-6}\mathrm{T}$ , northward
C.
$5 \times 10^{-6}\mathrm{T}$ , southward
D.
$2.5 \times 10^{-7}\mathrm{T}$ , northward
Q24 Allen MAGNETIC FIELD & BIOT-SAVART LAW MCQ
The wire in the figure carries a current i and consists of a circular arc of radius R and central angle $\frac{\pi}{2}$ rad, and two straight sections whose extensions intersect the centre C of the arc. The magnetic field $\vec{B}$ that the current produces at C is :-
A.
$\left|\vec{B}\right|=\frac{\mu_{0}i}{8R}$ into the plane of the figure
B.
$\left|\vec{B}\right|=\frac{\mu_{0}i}{8R}$ out of the plane of the figure
C.
$\left|\vec{B}\right|=\frac{\mu_{0}i}{8\pi R}$ into the plane of the figure
D.
$\left|\vec{B}\right|=\frac{\mu_{0}i}{8\pi R}$ out of the plane of the figure
Q25 Allen AMPERE'S LAW MCQ
For the hollow thin cylindrical current carrying pipe which statement is correct: -
A.
magnetic field inside the pipe is not zero
B.
magnetic field outside the pipe is zero
C.
electric field outside the pipe is zero
D.
electric field on the surface of pipe is zero