1
WB JEE 2019
+1
-0.25
A current 'I' is flowing along an infinite, straight wire, in the positive Z-direction and the same current is flowing along a similar parallel wire 5 m apart, in the negative Z-direction. A point P is at a perpendicular distance 3m from the first wire and 4m from the second. What will be magnitude of the magnetic field B of P?
A
$${5 \over {12}}({\mu _0}I)$$
B
$${7 \over {24}}({\mu _0}I)$$
C
$${5 \over {24}}{{{\mu _0}I} \over \pi }$$
D
$${{25} \over {288}}({\mu _0}I)$$
2
WB JEE 2019
+1
-0.25
A square conducting loop is placed near an infinitely long current carrying wire with one edge parallel to the wire as shown in the figure. If the current in the straight wire is suddenly halved, which of the following statements will be true?

"The loop will .........".
A
stay stationary
B
move towards the wire
C
move away from the wire
D
move parallel to the wire
3
WB JEE 2019
+2
-0.5
A particle with charge q moves with a velocity v in a direction perpendicular to the directions of uniform electric and magnetic fields, E and B respectively, which are mutually perpendicular to each other. Which one of the following gives the condition for which the particle moves undeflected in its original trajectory?

A
$$v = {E \over B}$$
B
$$v = {B \over E}$$
C
$$v = \sqrt {{E \over B}}$$
D
$$v = q{B \over E}$$
4
WB JEE 2018
+1
-0.25
A proton of mass m moving with a speed v (< < c, velocity of light in vacuum) completes a circular orbit in time T in a uniform magnetic field. If the speed of the proton is increased to $$\sqrt 2$$ v, what will be time needed to complete the circular orbit?
A
$$\sqrt 2$$T
B
T
C
$${{T \over {\sqrt 2 }}}$$
D
$${{T \over 2}}$$
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