1
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Four equal charges of value + Q are placed at any four vertices of a regular hexagon of side 'a'. By suitably choosing the vertices, what can be maximum possible magnitude of electric field at the centre of the hexagon?
A
$${Q \over {4\pi {\varepsilon _0}{a^2}}}$$
B
$${{\sqrt 2 Q} \over {4\pi {\varepsilon _0}{a^2}}}$$
C
$${{\sqrt 3 Q} \over {4\pi {\varepsilon _0}{a^2}}}$$
D
$${{2Q} \over {4\pi {\varepsilon _0}{a^2}}}$$
2
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
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
$${{T \over 2}}$$
3
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A uniform current is flowing along the length of an infinite, straight, thin, hollow cylinder of radius R. The magnetic field B produced at a perpendicular distance d from the axis of the cylinder is plotted in a graph. Which of the following figures looks like the plot?
A
WB JEE 2018 Physics - Magnetism Question 19 English Option 1
B
WB JEE 2018 Physics - Magnetism Question 19 English Option 2
C
WB JEE 2018 Physics - Magnetism Question 19 English Option 3
D
WB JEE 2018 Physics - Magnetism Question 19 English Option 4
4
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A circular loop of radius r of conducting wire connected with a voltage source of zero internal resistance produces a magnetic field B at its centre. If instead, a circular loop of radius 2r, made of same material, having the same cross-section is connected to the same voltage source, what will be the magnetic field at its centre?
A
$${B \over 2}$$
B
$${B \over 4}$$
C
2B
D
B
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