#### Electrostatics One Mark Questions

12th Standard EM

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 25
25 x 1 = 25
1. Two identical point charges of magnitude –q are fi xed as shown in the fi gure below. A third charge +q is placed midway between the two charges at the point P. Suppose this charge +q is displaced a small distance from the point P in the directions indicated by the arrows, in which direction(s) will +q be stable with respect to the displacement

(a)

A1 and A2

(b)

B1 and B2

(c)

both directions

(d)

No stable

2. Which charge configuration produces a uniform electric field?

(a)

point Charge

(b)

infinite uniform line charge

(c)

uniformly charged infinite plane

(d)

uniformly charged spherical shell

3. If voltage applied on a capacitor is increased from V to 2V, choose the correct conclusion

(a)

Q remains the same, C is doubled

(b)

Q is doubled, C doubled

(c)

C remains same, Q doubled

(d)

Both Q and C remain same

4. Two metallic spheres of radii 1 cm and 3 cm are given charges of -1 x 10-2 C and 5 x 10-2 C respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is

(a)

3 × 10-2 C

(b)

4 × 10-2 C

(c)

1 × 10-2 C

(d)

2 × 10-2 C

5. Based on Franklin's convention amber rods are_________.

(a)

positively charged

(b)

negatively charged

(c)

neutral

(d)

none of the above

6. The value of constant 'K' in coulomb law is

(a)

0.9 x 109 Nm2 C2

(b)

9 x 10-9 Nm2C2

(c)

9 x 109 Nm-2 C-2

(d)

9 x 109 Nm2 C-2

7. The electrostatic force is always greater in magnitude than gravitational force for_________ object.

(a)

bigger size

(b)

smaller size

(c)

medium size

(d)

all the above

8. The relative permittivity of water is _______.

(a)

εr= 70

(b)

εr=75

(c)

εr=80

(d)

εr=85

9. Which one of these is a vector quantity?

(a)

Electric charge

(b)

Electric field

(c)

Electric flux

(d)

Electric potential

10. The electric field created by a _________ is basically a non-uniform electric field.

(a)

Test charge

(b)

Positive charge

(c)

Negative charge

(d)

Point charge

11. Two condensers (capacitors) of capacity C1 and C2 are connected in parallel. A charge Q given to then is shared. The ratio of the charges Q is

(a)

$\frac { { C }_{ 2 } }{ { C }_{ 1 } }$

(b)

$\frac { { C }_{ 1 } }{ { C }_{ 2 } }$

(c)

C1.C2

(d)

$\frac { 1 }{ { C }_{ 1 }\times { C }_{ 2 } }$

12. Increasing the charge on the plates of a capacitor means

(a)

increasing the capacitance

(b)

increasing the potential difference between the plates

(c)

both (a) and (b) above

(d)

none of the above

13. An electric dipole placed at an angle in a nonuniform electric field experiences

(a)

neither a force nor a torque

(b)

torque

(c)

both force and torque

(d)

force only

14. Two copper spheres A and B of same size are charged to same potential. A is hollow and B is solid. Which of the two holds more charge?

(a)

Solid sphere cannot hold any charge

(b)

hollow sphere cannot hold any charge

(c)

both have zero charge

(d)

both have the same charge

15. A charge q is placed at the centre of a cubical box of side with top open. The flux of electric field through the surface of the cubical box is

(a)

Zero

(b)

$\frac { q }{ { \varepsilon }_{ 0 } }$

(c)

$\frac { q }{ 6{ \varepsilon }_{ 0 } }$

(d)

$\\ \frac { 5q }{ 6{ \varepsilon }_{ 0 } }$

16. The electric flux over a sphere of radius 1m is ф. If radius of the sphere were doubled without changing the charge enclosed, electric flux would become

(a)

(b)

$\\ \\ \\ \frac { \phi }{ 2 }$

(c)

$\\ \\ \\ \frac { \phi }{ 4 }$

(d)

ф

17. For continuous charge distributions, _____ methods can be used.

(a)

integration

(b)

differentiation

(c)

multiplication

(d)

18. Electrostatic force is stroger than gravitational force by_________.

(a)

2.23 x 1039 times

(b)

2.25 x 1039 times

(c)

2.27 x 1039 times

(d)

2.29 x 1039 times

19. Which of the following is a scalar quantity?

(a)

electric dipole moment

(b)

electric field intensity

(c)

electric potential

(d)

current density

20. The force between two charges at a particular distance in air is 36 N. If the distance between the charges is filled by a medium of dielectric constant 6, then the force is__________.

(a)

216 N

(b)

6 N

(c)

30 N

(d)

24 N

21. The value of relative permittivity of air is

(a)

8.854 x 10-12C2N-1m-2

(b)

9x109C2N-1m-2

(c)

1

(d)

8.854 x 1012

22. By using law of conservation of electric charge balance the following equations:
92U238 90Th234 ________.

(a)

2He4

(b)

1H3

(c)

1H2

(d)

1H1

23. Electric field intensity and electric potential are related by_________.

(a)

E=-$\frac{dV}{dt}$

(b)

E=-$\frac{dV}{dx}$

(c)

E=$\frac{dV}{dt}$

(d)

E=$\frac{-dx}{dV}$

24. Near a charged object A another earthed object B is placed. Charges are induced on B. If B is removed. After that the charge on A ________.

(a)

remains the same

(b)

decreases

(c)

increases

(d)

becomes zero

25. When an electric dipole is placed in a uniform external electric field parallel to the field, it will experience_________.

(a)

a torque but no force

(b)

a force but no torque

(c)

a torque as well as a force

(d)

neither a force nor a torque