Revision question Chapter 1.
1. The electric flux through the surface
a) fig (iv) is the largest
b) fig (iii) is the least c) fig (ii) is the same as
fig (iii) but is smaller than fig (iv)
d) is the same for all the figures
2. In comparison with the electrostatic force between
two electrons, the electrostatic force between two protons is:
(a) greater (b) smaller (c) zero (d) same.
3. Electric charges of 1μC, -1 μC and 2μC are placed in air at the corners A, B and C
respectively of an equilateral triangle ABC having length of each side 10 cm. The
resultant force on the charge at C is
a ) 0.9 N b). 1.8 N c). 2.7 N d). 3.6 N
4. A sphere S1 of radius r1 encloses total charge Q,If there is another concentric sphere
S2of radius r2(r2>r1) and there be no additional charge between S1 and S2.Find the ratio
of electric flux through S1 and S2
a )1 b) 0 c ) 1/2 d) Infinite
5. A system has two charges A=2.5×10 C B=−2.5×10−7C located at points A: (0, 0, -15
−7
cm) and B (0, 0, + 15 cm), respectively. What are the total charge and electric dipole
moment of the system?
6. Two charges q and -3q are placed fixed on x-axis separated by distance ‘d’. Where
should a third charge 2q be placed such that it will not experience any force?
7. Draw a plot showing variation of electric field with distance from the centre of a charge
spherical shell and uniformly charged solid sphere of radius R, having a charge of +Q on
its surface.
8. By using the Gauss law obtain the expression for electric field intensity due infinity
long straight uniformly charged wire.
Find the surface charge density of plane sheet of finite thickness having an electric field
of 300 N/C acting downward near the surface of sheet.
9. Four charge +q,+q,−q and −q are placed respectively at the
corners A,B,C and D of a square of side (a), arranged in the given
order. Calculate the magnitude and direction of electric field at
the center of the square where Q is a charge.
or
The electric field components in the figure
are Ex=αx1/2,Ey=0,Ez=0 where α=800N/m2. If a = 0.1 m is the side of cube then the charge
within the cube is:
10. 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.
11. Two point charges + q and -2q are placed at the vertices ‘B’
and ‘C’ of an equilateral triangle ABC of side as given in
the figure. Obtain the expression for (i) the magnitude and (ii) the direction of the
resultant electric field at the vertex A due to these two charges.
12. Two spherical conductors of radii Ra and R2 (R2 > R1) are charged. If they are
connected by a conducting wire, find out the ratio of the surface charge densities on
them.
