Physics-DPP-4-Electrostatics
PHYSICS Topic: ELECTROSTATICS Date:
1. A solid conducting sphere of radius a has a net positive charge 2Q. A conducting spherical shell of inner radius b and outer radius c is concentric with the solid sphere and has a net charge – Q. The surface charge density on the inner and outer surfaces of the spherical shell will be :
(a) –
2Q
4πb2
, Q
4πc2
(b) (b)
– Q
4πb2
, Q
4πc2
(c) (c)
0, Q
4πc2
(d) none of these
2. Three concentric conducting spherical shells carry charges as follows ; + Q on the inner shell, – 2Q on the middle shell and – 5Q on the outer shell. The charge on the inner surface of the outermost shell is :
(a) zero (b) + Q (c) – 2Q (d) – 3 Q
3. A thin, metallic spherical sheel contains a charge Q on it. A point charge q is placed at the centre of the shell and another charge q1 is placed outside it as shown in figure. All the three charges are positive. The force on the charge at the centre is :
(a) towards left (b) towards right (c) upward (d) zero
4. Two conducting plates A and B each having large surface area S (on one side) are placed parallel to each other. The plate A is given a charge q, while the plate B is neutral. Then the electric field at a point in between the plates is :
q q 2q 3 q
(a)
2Sε0
(b)
Sε0
(c)
Sε0
(d)
2 Sε0
5. Three charges Q, + q and + q are placed at the vertices of a right-angled isosceles triangle as shown. The net electrostatic energy of the configuration is zero, if Q is equal to :
(a)
(b)
(c) – 2q (d) + q
6. A point charge q is placed at a distance r from the centre O of an uncharged spherical shell of inner radius R and outer radius 2R. The distance r < R. The electric potential at the centre of the shell will be
:
(a)
q æç1 –
çè
1 ö÷
÷
q
(b)
(c)
q æç1
ç
1 ö÷
÷
(d)
q æç1
ç
1 ö÷
÷
4πε0 r
2R ø
4πε0 r
4πε0 èr
2R ø
4πε0 èr R ø
PHYSICS Topic: ELECTROSTATICS Date:
7. A solid conducting sphere of radius r is having a charge Q and a point charge q is at a distance d from the center of sphere as shown in the diagram. The electric potential inside the solid sphere is :
(a)
1 æçQ – q +
çè
q ö÷
÷
(b)
1 æçQ
ç
Q – q ö÷
÷
4πε0
r d ø
4πε0 è r d ø
(c)
1 æçQ +
çè
q ö÷
÷
(d) none of these
4πε0 r d ø
8. A conducting sphere A is surrounded by two concentric conducting hollow spheres B and C. A is given a positive charge q and C is earthed as shown in the figure. Choose the correct statement :
(a) charge density on A,B and C are same
q
(b) electric field just outside C is 4πε c2
(c) electric field outside C is zero
(d) potential inside A is zero
9. A conducting sphere having radius a is charged to a potential V1. Now it is surrounded by another neutral conducting spherical shell of radius b. The potential V2 acquired by the sphere after it is connected to shell by a thin conducting wire is :
(a) V a
b
(b) V b
a
(c) (c)
V1 (a + b)
b
(d) (d)
V1a
(a + b)
10. A charge q is distributed over two conectric hollow conducting spheres of radii r and R (> r) such that their surface charge densities are equal. The potential at their common centre is :
q (r + R)
q é1 1 ù
q (r + R)
(a) zero (b)
4πε 2 2 2
(c)
ê + ú
(d)
4πε 2 2
0 (r + R )
4πε0
êër R úû
0 (r + R )
PHYSICS Topic: ELECTROSTATICS Date:
1. (a)
2. (b)
Answer Key
3. (d) 4. (a)
5. (b)
6. (a)
7. (c)
8. (c) 9. (a)
10. (d)
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