1
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
For an ideal gas with initial pressure and volume pi and Vi respectively, a reversible isothermal expansion happens, when its volume becomes V0. Then, it is compressed to its original volume Vi by a reversible adiabatic process. If the final pressure is pf, then which of the following statement(s) is/are true?
A
pf = pi
B
pf > pi
C
pf < pi
D
$${{{p_f}} \over {{V_0}}}\, = \,{{{p_i}} \over {{V_i}}}$$
2
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A point charge $$-$$ q is carried from a point A to another point B on the axis of a charged ring of radius r carrying a charge + q. If the point A is at a distance $${4 \over 3}r$$ from the centre of the ring and the point B is $${3 \over 4}r$$ from the centre but on the opposite side, what is the net work that need to be done for this?
A
$$ - {7 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}$$
B
$$ - {1 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}$$
C
$${7 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}$$
D
$${1 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}$$
3
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Consider a region in free space bounded by the surfaces of an imaginary cube having sides of length a as shown in the figure. A charge + Q is placed at the centre O of the cube. P is such a point outside the cube that the line OP perpendicularly intersects the surface ABCD at R and also OR = RP = a/2. A charge + Q is placed at point P also. What is the total electric flux through the five faces of the cube other than ABCD?

WB JEE 2018 Physics - Electrostatics Question 18 English
A
$${Q \over {{\varepsilon _0}}}$$
B
$${5Q \over {{6\varepsilon _0}}}$$
C
$${10Q \over {{6\varepsilon _0}}}$$
D
zero
4
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
$${{2Q} \over {4\pi {\varepsilon _0}{a^2}}}$$
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