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Physics M.C.Q (1 Marks)

Magnetism and Matter · Rajasthan Board (RBSE) STD 12 Science (Rajasthan - English Medium). 24 questions.

Questions

M.C.Q (1 Marks)

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24 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
Relative electrical conductivity and relative magnetic permeability of a substance is $\epsilon_r$ and $\mu_r$ What are the probable values of these quantities for any dimagnetic substance?
Answer
(a)$\epsilon_r=1.5 \quad \mu_r=0.5$
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Question 21 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 :
Answer
(b) $2.4 \times 10^{-4} T$
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Question 31 Mark
When two bar magnets are coaxially placed at some distance from each other, then no torque works because:
Answer
(d)Forces on their poles are along the same line
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Question 41 Mark
A rod of length L and magnetic moment M is bent to form a semicircle. Now its magnetic moment will be:
Answer
(b) $\frac{2 M }{\pi}$
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Question 51 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 :
Answer
(b) $150 \hat{k} N- m$
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Question 61 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 :
Answer
(d)0.1 m
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Question 81 Mark
If paramagnetic susceptibility $\chi$ of a substance is 9 then its relative permeability $\mu_r$ is :
Answer
(a)10
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Question 111 Mark
Which of the following statements is not correct?
Answer
(d)Magnetic susceptibility of ferromagnetic subs- tances is zero at Curie temperature.
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Question 121 Mark
In an electromagnet, core is made of soft iron because:
Answer
(b) its susceptibility is more but retentivity is less.
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Question 151 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 :
Answer
(b) $-\vec{F}$
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Question 161 Mark
If distance between two magnetic poles of strength (1 A-m) is 1 metre, then magnitude of force acting between them is:
Answer
(c )$10^{-7} N$
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Question 171 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:
Answer
(b) 2:1
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Question 181 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:
Answer
(b) $\frac{m}{4}$
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Question 191 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:
Answer
(d)$\frac{m}{\sqrt{2}}$
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Question 201 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:
Answer
(d)$r^2$
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Question 221 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:
Answer
(a)$\sqrt{3} W$
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Question 231 Mark
A bar magnet of magnetic moment $m$ when kept in a maenetic field of intensity $\vec{B}$ experiences a torgue:
Answer
(a)$\vec{m} \times \overrightarrow{ B }$
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Question 241 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:
Answer
(b) east-west
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