Question 12

A charge of 8 mC is located at the origin. Calculate the work done in taking a small charge of -2 x 10^{-9} C from a point P (0, 0, 3 cm) to a point Q (0, 4 cm, 0), via a point R (0, 6 cm, 9 cm).

Answer

Charge located at the origin, q = 8 mC= 8 × 10 ^{- 3} C

Magnitude of a small charge, which is taken from a point P to point R to point Q, q_{1} = - 2 × 10 ^{- 9 }C

All the points are represented in the given figure.

Point P is at a distance, d_{1} = 3 cm, from the origin along z-axis.

Point Q is at a distance, d_{2} = 4 cm, from the origin along y-axis.

Potential at point P,

Potential at point Q,

Work done (W) by the electrostatic force is independent of the path.

Therefore, work done during the process is 1.27 J.

- Q:-
An infinite line charge produces a field of 9 × 10

^{4}N/C at a distance of 2 cm. Calculate the linear charge density. - Q:-
What is the force between two small charged spheres having charges of 2 x 10

^{-7}C and 3 x 10^{-7}C placed 30 cm apart in air? - Q:-
A polythene piece rubbed with wool is found to have a negative charge of 3 × 10

^{−7}C.(a) Estimate the number of electrons transferred (from which to which?)

(b) Is there a transfer of mass from wool to polythene?

- Q:-
A parallel plate capacitor with air between the plates has a capacitance of 8 pF (1pF = 10

^{-12}F). What will be the capacitance if the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6? - Q:- A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field B at the centre of the coil?
- Q:-
A 600 pF capacitor is charged by a 200 V supply. It is then disconnected from the supply and is connected to another uncharged 600 pF capacitor. How much electrostatic energy is lost in the process?

- Q:-
A regular hexagon of side 10 cm has a charge 5 µC at each of its vertices. Calculate the potential at the centre of the hexagon.

- Q:-
A point charge +10 μC is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)

- Q:-
A point charge of 2.0 μC is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?

- Q:-
A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 10

^{3}N/C and points radially inward, what is the net charge on the sphere?

- Q:-
(a) In a metre bridge [Fig. 3.27], the balance point is found to be at 39.5 cm from the end

*A*, when the resistor*Y*is of 12.5**Ω**. Determine the resistance of*X*. Why are the connections between resistors in a Wheatstone or meter bridge made of thick copper strips?(b) Determine the balance point of the bridge above if

*X*and*Y*are interchanged.(c) What happens if the galvanometer and cell are interchanged at the balance point of the bridge? Would the galvanometer show any current?

- Q:-
A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 10

^{3}N/C and points radially inward, what is the net charge on the sphere? - Q:-
An oil drop of 12 excess electrons is held stationary under a constant electric field of 2.55 × 10

^{4}N C^{−1}in Millikan’s oil drop experiment. The density of the oil is 1.26 g cm^{−3}. Estimate the radius of the drop. (g = 9.81 m s^{−2}; e = 1.60 × 10^{−19}C). - Q:-
Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is 8.0 × 103 N m2/C.

(a) What is the net charge inside the box?

(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or Why not?

- Q:-
Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude 17.0 × 10

^{−22}C/m^{2}. What is E:(a) in the outer region of the first plate,

(b) in the outer region of the second plate, and

(c) between the plates?

- Q:-
(a) Using the Bohr’s model calculate the speed of the electron in a hydrogen atom in the n = 1, 2, and 3 levels.

(b) Calculate the orbital period in each of these levels.

- Q:-
A closely wound solenoid 80 cm long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8 cm. If the current carried is 8.0 A, estimate the magnitude of B inside the solenoid near its centre.

- Q:-
An electric dipole with dipole moment 4 × 10

^{−9}C m is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 10^{4}N C^{−1}. Calculate the magnitude of the torque acting on the dipole. - Q:-
What is the force between two small charged spheres having charges of 2 x 10

^{-7}C and 3 x 10^{-7}C placed 30 cm apart in air? - Q:-
Three capacitors each of capacitance 9 pF are connected in series.

(a) What is the total capacitance of the combination?

(b) What is the potential difference across each capacitor if the combination is connected to a 120 V supply?

Suma Bharadhwaj
2020-09-03 16:22:05

Good job....it extremely helps

Makfi Khan
2019-10-12 20:24:30

Thank you so much. Nicely explained.

nishma
2019-06-28 20:37:50

l like the mode of explanation you taken in this question

Sunita
2019-06-09 21:06:08

Third point ka kya hua

Ham majboor hai
2019-05-26 10:11:42

Chodu banavat hai

AWESOME SITE
2019-02-14 17:09:06

">AWESOME SITE

yyy
2018-07-28 21:07:15

copied

xxx
2018-06-16 20:05:36

outstanding answer with outstanding explanation

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