M.C.Q (1 Marks)

MCQ 11 Mark

A bar magnet of magnetic moment $m$ when kept in a maenetic field of intensity $\vec{B}$ experiences a torgue:

✓
$\vec{m} \times \overrightarrow{ B }$
B
$\overrightarrow{ B } \times \vec{m}$
C
$\vec{m} \cdot \overrightarrow{B}$
D
$\frac{\vec{m} \times \vec{B}}{\sqrt{2}}$

Answer

Correct option: A.

$\vec{m} \times \overrightarrow{ B }$

(a)$\vec{m} \times \overrightarrow{ B }$

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MCQ 21 Mark

One bar magnet is kept in the direction of north-south such that its north pole is towards north.The direction of points of zero magnetic field is towards which side of the centre of the magnet:

A
north-south
✓
east-west
C
north-east and south-west
D
north-west and south-cast

Answer

Correct option: B.

east-west

(b) east-west

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MCQ 31 Mark

Relative electrical conductivity and relative magnetic permeability of a substance is $\in_r$ and $\mu_r$ What are the probable values of these quantities for any dimagnetic substance?

✓
$\in_r=1.5 \quad \mu_r=0.5$
B
$\in_r=0.5 \quad \mu_r=0.5$
C
$\in_r=1.5 \quad \mu_r=1.5$
D
$\in_r=0.5 \quad \mu_r=1.5$

Answer

Correct option: A.

$\in_r=1.5 \quad \mu_r=0.5$

(a)$\in_r=1.5 \quad \mu_r=0.5$

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MCQ 41 Mark

Magnetic moment of a small bar magnet is $1.2 A- m ^2$. Magnetisation field at a distance of 0.1 m on its axis is :

A
$1.2 \times 10^{-4} T$
✓
$2.4 \times 10^{-4} T$
C
$2.4 \times 10^{4} T$
D
$1.2 \times 10^{4} T$

Answer

Correct option: B.

$2.4 \times 10^{-4} T$

(b) $2.4 \times 10^{-4} T$

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MCQ 51 Mark

When two bar magnets are coaxially placed at some distance from each other, then no torque works because:

A
There is no force on its poles
B
Forces acting on their poles is parallel and their lines of action do not coincide.
C
Forces on their poles are perpendicular to each other
✓
Forces on their poles are along the same line

Answer

Correct option: D.

Forces on their poles are along the same line

(d)Forces on their poles are along the same line

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MCQ 61 Mark

A rod of length L and magnetic moment M is bent to form a semicircle. Now its magnetic moment will be:

A
M
✓
$\frac{2 M }{\pi}$
C
$\frac{ M }{\pi}$
D
$M \pi$

Answer

Correct option: B.

$\frac{2 M }{\pi}$

(b) $\frac{2 M }{\pi}$

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MCQ 71 Mark

A magnet whose magnetic moment is $50 \hat{i} Am ^2$. It is kept in an magnetic field $\vec{B}=(0.5 \hat{i}+3.0 \hat{j}) T$ along the direction of $x$-axis. The torque acting on the magnet is :

A
$175 \hat{k} N- m$
✓
$150 \hat{k} N- m$
C
$75 \hat{k} N- m$
D
$25 \sqrt{37} \hat{k} N- m$

Answer

Correct option: B.

$150 \hat{k} N- m$

(b) $150 \hat{k} N- m$

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MCQ 81 Mark

A bar magnet of magnetic moment $3.0 A- m ^2$ is kept in an uniform magnetic induction of $2 \times 10^{-5} T$. If each pole of the magnet experiences a force of $6 \times 10^{-4} N$, then length of the magnet is :

A
0.5 m
B
0.3 m
C
0.2 m
✓
0.1 m

Answer

Correct option: D.

0.1 m

(d)0.1 m

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MCQ 91 Mark

1 tesla is equal to:

A
$10^{-7}$ Gauss
B
$10^{-4}$ Gauss
✓
$10^{4}$ Gauss
D
$10^{-8}$ Gauss

Answer

Correct option: C.

$10^{4}$ Gauss

(c )$10^{4}$ Gauss

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MCQ 101 Mark

If paramagnetic susceptibility $\chi$ of a substance is 9 then its relative permeability $\mu_r$ is :

✓
10
B
0.1
C
9
D
0.11

Answer

Correct option: A.

(a)10

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MCQ 111 Mark

For ferromagnetic substances:

✓
permeability is high and susceptibility is high and positive
B
permeability is high but susceptibility is negative and less.
C
permeability is low but susceptibility is positive and high.
D
permeability is very less and susceptibility is negative and less

Answer

Correct option: A.

permeability is high and susceptibility is high and positive

(a)permeability is high and susceptibility is high and positive

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MCQ 121 Mark

Unit of relative permeability is:

A
weber/m
✓
without unit
C
henry/m
D
ampere/m

Answer

Correct option: B.

without unit

(b) without unit

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MCQ 131 Mark

Which of the following statements is not correct?

A
Dimagnetism is characteristic of all substances
B
At Curie temperature, ferromagnetic substances become paramagnetic.
C
Those atoms whose orbits are incomplete are paramagnetic.
✓
Magnetic susceptibility of ferromagnetic subs- tances is zero at Curie temperature.

Answer

Correct option: D.

Magnetic susceptibility of ferromagnetic subs- tances is zero at Curie temperature.

(d)Magnetic susceptibility of ferromagnetic subs- tances is zero at Curie temperature.

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MCQ 141 Mark

In an electromagnet, core is made of soft iron because:

A
its susceptibility and retentivity is more.
✓
its susceptibility is more but retentivity is less.
C
susceptibility and retentivity both are less.
D
retentivity is more but susceptibility is less.

Answer

Correct option: B.

its susceptibility is more but retentivity is less.

(b) its susceptibility is more but retentivity is less.

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MCQ 151 Mark

Which type of substance is copper?

✓
Dimagnetic
B
Paramagnetic
C
Ferromagnetic
D
Non-magnetic

Answer

Correct option: A.

Dimagnetic

(a)Dimagnetic

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MCQ 161 Mark

Magnetic needle can remain safe in:

✓
iron box
B
wooden box
C
metal box
D
none of these

Answer

Correct option: A.

iron box

(a)iron box

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MCQ 171 Mark

A square current loop is suspended in a uniform magnetic field which is located at its base. If force on one arm of the loop is $\vec{F}$. Then the resultant force on rest three arms is :

A
$3 \vec{F}$
✓
$-\vec{F}$
C
$-3 \vec{F}$
D
$\overrightarrow{ F }$

Answer

Correct option: B.

$-\vec{F}$

(b) $-\vec{F}$

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MCQ 181 Mark

If distance between two magnetic poles of strength (1 A-m) is 1 metre, then magnitude of force acting between them is:

A
$4 \pi \times 10^{-7} N$
B
$\frac{4 \pi}{10^{-7}} N$
✓
$10^{-7} N$
D
$\frac{10^{-7}}{4 \pi} N$

Answer

Correct option: C.

$10^{-7} N$

(c )$10^{-7} N$

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MCQ 191 Mark

Ratio between intensities of magnetic fields due to points situated on axial and non-axial positions of a small magnet at distance from it is:

A
1:2
✓
2:1
C
1:4
D
4:1

Answer

Correct option: B.

2:1

(b) 2:1

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MCQ 201 Mark

Magnetic moment of a thin bar magnet is M. If it is cut first perpendicular to length and then perpendicular to breadth, then magnetic moment of obtained piece is:

A
$\frac{m}{2}$
✓
$\frac{m}{4}$
C
m
D
2m

Answer

Correct option: B.

$\frac{m}{4}$

(b) $\frac{m}{4}$

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MCQ 211 Mark

Length of a magnetic iron wire is / and its magnetic moment is m. If on moulding it in the form of L, its all arms are of equal sizes, then magnetic moment of new shape will be:

A
m
B
$\frac{m}{2}$
C
$\sqrt{2 m}$
✓
$\frac{m}{\sqrt{2}}$

Answer

Correct option: D.

$\frac{m}{\sqrt{2}}$

(d)$\frac{m}{\sqrt{2}}$

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MCQ 221 Mark

Current is flowing in a circular coil of radius r. There are n turns in the coil. Its magnetic moment varies with r. As:

A
$\frac{1}{r^2}$
B
$\frac{1}{r}$
C
r
✓
$r^2$

Answer

Correct option: D.

$r^2$

(d)$r^2$

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MCQ 231 Mark

Vertical component of earth's magnetic field is zero:

A
at magnetic poles
B
at geographic poles
C
at every place
✓
at magnetic axis

Answer

Correct option: D.

at magnetic axis

(d)at magnetic axis

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MCQ 241 Mark

A magnetic needle kept parallel to a magnetic field requires a work W to be rotated by 60. The necessary torque required to keep the needle in this position is:

✓
$\sqrt{3} W$
B
W
C
$\frac{\sqrt{3}}{2} W$
D
2W

Answer

Correct option: A.

$\sqrt{3} W$

(a)$\sqrt{3} W$

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Physics M.C.Q (1 Marks)

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