4. Moving charges and magnetism - CBSE STD 12 Science Physics Questions

Q 1M.C.Q (1 Marks)1 Mark

A tightly wound $100$ turns coil of radius $10 \mathrm{~cm}$ carries a current of $7 \mathrm{~A}$. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $4 \pi \times 10^{-7} \mathrm{SI}$ units):

A
$4.4 \mathrm{~T}$
✓
$4.4 \mathrm{mT}$
C
$44 \mathrm{~T}$
D
$44 \mathrm{mT}$

Answer: B.

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Q 2M.C.Q (1 Marks)1 Mark

In a uniform magnetic field of $0.049 \mathrm{~T}$, a magnetic needle performs $20$ complete oscillations in $5$ seconds as shown. The moment of inertia of the needle is $9.8 \times 10^{-5} \mathrm{~kg} \mathrm{~m}^2$. If the magnitude of magnetic moment of the needle is $x \times 10^{-5} \mathrm{Am}^2$, then the value of ' $x$ ' is :

A
$128 \pi^2$
B
$50 \pi^2$
✓
$1280 \pi^2$
D
$5 \pi^2$

Answer: C.

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Q 3M.C.Q (1 Marks)1 Mark

A very long conducting wire is bent in a semicircular shape from $A$ to $B$ as shown in figure. The magnetic field at point $P$ for steady current configuration is given by:

A
$\frac{\mu_0 i }{4 R }\left[1-\frac{2}{\pi}\right]$ pointed into the page
B
$\frac{\mu_0 i }{4 R }$ pointed into the page
C
$\frac{\mu_0 i }{4 R }$ pointed away from the page
✓
$\frac{\mu_0 i }{4 R }\left[1-\frac{2}{\pi}\right]$ pointed away from page

Answer: D.

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Q 4M.C.Q (1 Marks)1 Mark

A wire carrying a current $I$ along the positive $x$-axis has length $L$ It is kept in a magnetic field $\overrightarrow{ B }=(2 \hat{ i }+3 \hat{ j }-4 \hat{ k }) T$. The magnitude of the magnetic force acting on the wire is $..........IL$

A
$\sqrt{3}$
B
$3$
C
$\sqrt{5}$
✓
$5$

Answer: D.

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Q 5M.C.Q (1 Marks)1 Mark

Given below are two statements$:$

Statement $I:$ Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element (IdI) of a current carrying conductor only.

Statement $II :$ Biot-Savart's law is analogous to Coulomb's inverse square law of charge $q$, with the former being related to the field produced by a scalar source, Idl while the latter being produced by a vector source, $q$. In light of above statements choose the most appropriate answer from the options given below:

A
Both Statement $I$ and Statement $II$ are incorrect
✓
Statement $I$ is correct and Statement $II$ is incorrect
C
Statement $I$ is incorrect and Statement $II$ is correct
D
Both Statement $I$ and Statement $II$ are correct

Answer: B.

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4. Moving charges and magnetism question types

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