1
CBSE 12th Physics (Term 1) Paper 2021-22
+0.77
-0
A straight conducting rod of length l and mass m is suspended in a horizontal plane by a pair of flexible strings in a magnetic field of magnitude B. To remove the tension in the supporting strings, the magnitude of the current in the wire is
A
$${{mgB} \over l}$$
B
$${{mgl} \over B}$$
C
$${{mg} \over {lB}}$$
D
$${{lB} \over {mg}}$$
2
CBSE 12th Physics (Term 1) Paper 2021-22
+0.77
-0
A constant current is flowing through a solenoid. An iron rod is inserted in the solenoid along its axis. Which of the following quantities will not increase?
A
The magnetic field at the centre
B
The magnetic flux linked with the solenoid
C
The rate of heating
D
The self-inductance of the solenoid
3
CBSE 12th Physics (Term 1) Paper 2021-22
+0.77
-0
A proton and an alpha particle move in circular orbits in a uniform magnetic field. Their speeds are in the ratio of 9 : 4. The ratio of radii of their circular orbits $$\left( {{{{r_p}} \over {{r_{alpha}}}}} \right)$$ is
A
$${3 \over 4}$$
B
$${4 \over 3}$$
C
$${8 \over 9}$$
D
$${9 \over 8}$$
4
CBSE 12th Physics (Term 1) Paper 2021-22
+0.77
-0
Assertion (A) : When radius of a current carrying loop is doubled, its magnetic moment becomes four times.

Reason (R) : The magnetic moment of a current carrying loop is directly proportional to the area of the loop.
A
Both (A) & (R) are true and (R) is correct explanation of (A).
B
Both (A) & (R) are true and (R) is not correct explanation of (A).
C
(A) is true but (R) is false.
D
(A) is false and (R) is also false.
Class 12 Subjects
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
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