TEST 2 : chapter 1 physics class 12 (CBSE)

QUESTION
Why must electrostatic field be normal to the surface at every point of a charged conductor?
(Delhi 2012).

QUESTION
A charge ‘q’ is placed at the centre of a cube of side l. What is the electric flux passing
through each face of the cube? (All India 2012)

QUESTION
A charge ‘q’ is placed at the centre of a cube of side l. What is the electric flux passing
through two opposite faces of the cube? (All India)

QUESTION
Depict the direction of the magnetic field lines due to a circular current carrying loop.
(Comptt. Delhi 2012)

QUESTION
What is the direction of the electric field at the surface of a charged conductor having charge
density σ < 0? (Comptt. Delhi 2012)

QUESTION
Two charges of magnitudes – 2Q and + Q are located at points (a, 0) and (4a,0) respectively.
What is the electric flux due to these charges through a sphere of radius ‘3a’ with its centre at
the origin? (All India 2013)

QUESTION
Write the expression for the work done on an electric dipole of dipole moment p in turning it
from its position of stable equilibrium to a position of unstable equilibrium in a uniform
electric
field E. (Comptt. Delhi 2013)

QUESTION
What is the electric flux through a cube of side 1 cm which encloses an electric dipole?
(Delhi 2015)

QUESTION
Why are electric field lines perpendicular at a point on an equipotential surface of a
conductor? (Comptt. All India 2015)

QUESTION

Is the potential difference VA – VB positive, negative or zero? (Delhi 2016)

QUESTION
How does the electric flux due to a point charge enclosed by a spherical Gaussian surface get
affected when its radius is increased? (Delhi 2016)

QUESTION
Show on a plot the nature of variation of the

 Electric field (E) and

 potential (V), of a (small) electric dipole with the distance (r) of the field point
from the centre of the dipole. (Comptt. Outside Delhi 2016)

QUESTION
Does the charge given to a metallic sphere depend on whether it is hollow or solid? Give
reason for your answer

QUESTION
A point charge +Q is placed in the vicinity of a conducting surface. Draw the electric field
lines between the surface and the charge.
(Comptt. Outside Delhi 2017)

QUESTION
Define electric flux. Write its S.I. unit.
A charge q is enclosed by a spherical surface of radius R. If the radius is reduced to half, how
would the electric flux through the surface change? (All India 2009)

QUESTION
A spherical conducting shell of inner radius rx and outer radius r2 has a charge ‘Q’. A charge
‘q’ is placed at the centre of the shell.
(a) What is the surface charge density on the
(i) inner surface,
(ii) outer surface of the shell?
(b) Write the expression for the electric field at a point x > r2 from the centre of the shell. (All
India 2010)
QUESTION
A thin straight infinitely long conducting wire having charge density X is enclosed by a
cylindrical surface of radius r and length l, its axis coinciding with the length of the wire.
Find the expression for the electric flux through the surface of the cylinder. (All India 2011)

QUESTION
Plot a graph showing the variation of coulomb force (F) versus (1r2), where r is the distance
between the two charges of each pair of charges : (1µC, 2µC) and (2µC, – 3µC). Interpret the
graphs obtained. (All India 2010)

QUESTION
A hollow cylindrical box of length 1m and area of cross-section 25 cm2 is placed in a three
dimensional coordinate system as shown in the figure. The electric field in the region is given
by E→=50xi^ where E is in NC-1 and x is in metres. Find

 Net flux through the cylinder.

 Charge enclosed by the cylinder. (Delhi 2013)

QUESTION

Given a uniform electric field , find the flux of this field through a
square of 10 cm on a side whose plane is parallel to the y-z plane. What would be the flux
through the same square if the plane makes a 30° angle with the x-axis? (Delhi 2014)

QUESTION
Given a uniform electric field E→ = 2 × 103 i^ N/ C, find the flux of this field through a
square of side 20 cm, whose plane is parallel to the y-z plane. What would be the flux
through the same square, if the plane makes an angle of 30° with the x-axis? (Delhi 2014)

QUESTION
Given a uniform electric field E→=4×103i^ N/C. Find the flux of this field through a
square of 5 cm on a side whose plane is parallel to the Y-Z plane. What would be the flux
through the same square if the plane makes a 30° angle with the x-axis? (Delhi 2014)

QUESTION
A small metal sphere carrying charge +Q is located at the centre of a spherical cavity in a
large uncharged metallic spherical shell. Write the charges on the inner and outer surfaces of
the shell. Write the expression for the electric field at the point P1 (Comptt. Delhi)

QUESTION
An electric dipole is placed in a uniform electric field E→ with its dipole moment p⃗ parallel
to the field. Find
(i) the work done in turning the dipole till its dipole moment points in the direction
opposite to E→ .
(ii) the orientation of the dipole for which the torque acting on it becomes maximum.
(Comptt. All India 2014)

QUESTION
A sphere S1 of radius r1 encloses a net charge Q. If there is another concentric sphere S2 of
radius r2 (r2 > r,) enclosing charge 2Q, find the ratio of the electric flux through S1 and S2.
How will the electric flux through sphere S1 change if a medium of dielectric constant K is
introduced in the space inside S2 in place of air? (Comptt. All India 2014)

QUESTION
Define the term ‘electric flux’. Write its S.I. units. What is the flux due to electric
field E→=3×103i^ N/C through a square of side 10 cm, when it is held normal to if?
(Comptt. All India 2015)

QUESTION
A thin conducting spherical shell of radius R has charge Q spread uniformly over its surface.
Using Gauss’s law, derive an expression for an electric field at a point outside the shell.
Draw a graph of electric field E(r) with distance r from the centre of the shell for 0 ≤ r ≤ ∞
QUESTION
State Gauss’ law in electrostatics. Using this law derive an expression for the electric field
due to a uniformly changed infinite plane sheet.

QUESTION
State ‘Gauss law’ in electrostatics. Use this law to derive an expression for the electric field
due to an infinitely long straight wire of linear charge density λ cm-1

QUESTION
A positive point charge (+ q) is kept in the vicinity of an uncharged conducting plate. Sketch
electric field lines originating from the point on to the surface of the plate.
Derive the expression for the electric field at the surface of a charged conductor. (All India)

QUESTION
Use Gauss’s law to derive the expression for the electric field between two uniformly charged
large parallel sheets with surface charge densities a and -a respectively. (All India)

QUESTION
State Gauss’s law.
A thin straight infinitely long conducting wire of linear charge density ‘X’ is enclosed by a
cy¬lindrical surface of radius V and length ‘l’—its axis coinciding with the length of the
wire. Obtain the expression for the electric field, indi¬cating its direction, at a point on the
surface of the cylinder. (Comptt. Delhi 2012)