1
JEE Main 2022 (Online) 25th June Evening Shift
+4
-1

A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of magnetic field will be equal to

A
B
B
2B
C
4B
D
$${B \over 2}$$
2
JEE Main 2022 (Online) 25th June Morning Shift
+4
-1

A long straight wire with a circular cross-section having radius R, is carrying a steady current I. The current I is uniformly distributed across this cross-section. Then the variation of magnetic field due to current I with distance r (r < R) from its centre will be :

A
B $$\propto$$ r2
B
B $$\propto$$ r
C
B $$\propto$$ $${1 \over {{r^2}}}$$
D
B $$\propto$$ $${1 \over {{r}}}$$
3
JEE Main 2022 (Online) 24th June Evening Shift
+4
-1

A proton, a deutron and an $$\alpha$$-particle with same kinetic energy enter into a uniform magnetic field at right angle to magnetic field. The ratio of the radii of their respective circular paths is :

A
1 : $$\sqrt 2$$ : $$\sqrt 2$$
B
1 : 1 : $$\sqrt 2$$
C
$$\sqrt 2$$ : 1 : 1
D
1 : $$\sqrt 2$$ : 1
4
JEE Main 2022 (Online) 24th June Morning Shift
+4
-1

Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : In an uniform magnetic field, speed and energy remains the same for a moving charged particle.

Reason (R) : Moving charged particle experiences magnetic force perpendicular to its direction of motion.

A
Both (A) and (R) are true and (R) is the correct explanation of (A).
B
Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
C
(A) is true but (R) is false.
D
(A) is false but (R) is true.
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