Question

Charges are placed on the vertices of a square as shown. Let $$\overrightarrow E $$ be the electric field and $$V$$ the potential at the centre. If the charges on $$A$$ and $$B$$ are interchanged with those on $$D$$ and $$C$$ respectively, then
Electric Field mcq question image

A. $$\overrightarrow E $$ changes, $$V$$ remains unchanged  
B. $$\overrightarrow E $$ remains unchanged, $$V$$ changes
C. both $$\overrightarrow E $$ and $$V$$ change
D. $$\overrightarrow E $$ and $$V$$ remain unchanged
Answer :   $$\overrightarrow E $$ changes, $$V$$ remains unchanged
Solution :
As shown in the figure, the resultant electric fields before and after interchanging the charges will have the same magnitude, but opposite directions.
Also, the potential will be same in both cases as it is a scalar quantity.
Electric Field mcq solution image

Releted MCQ Question on
Electrostatics and Magnetism >> Electric Field

Releted Question 1

A hollow metal sphere of radius $$5 cms$$  is charged such that the potential on its surface is $$10\,volts.$$  The potential at the centre of the sphere is

A. zero
B. $$10\,volts$$
C. same as at a point $$5 cms$$  away from the surface
D. same as at a point $$25 cms$$  away from the surface
Releted Question 2

Two point charges $$ + q$$  and $$ - q$$  are held fixed at $$\left( { - d,o} \right)$$  and $$\left( {d,o} \right)$$  respectively of a $$x-y$$  coordinate system. Then

A. The electric field $$E$$ at all points on the $$x$$-axis has the same direction
B. Electric field at all points on $$y$$-axis is along $$x$$-axis
C. Work has to be done in bringing a test charge from $$\infty $$ to the origin
D. The dipole moment is $$2qd$$  along the $$x$$-axis
Releted Question 3

Three positive charges of equal value $$q$$ are placed at the vertices of an equilateral triangle. The resulting lines of force should be sketched as in

A. Electric Field mcq option image
B. Electric Field mcq option image
C. Electric Field mcq option image
D. Electric Field mcq option image
Releted Question 4

A uniform electric field pointing in positive $$x$$-direction exists in a region. Let $$A$$ be the origin, $$B$$ be the point on the $$x$$-axis at $$x = + 1cm$$   and $$C$$ be the point on the $$y$$-axis at $$y = + 1cm.$$   Then the potentials at the points $$A,B$$  and $$C$$ satisfy:

A. $${V_A} < {V_B}$$
B. $${V_A} > {V_B}$$
C. $${V_A} < {V_C}$$
D. $${V_A} > {V_C}$$

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