Question 23

An infinite line charge produces a field of 9 × 10^{4} N/C at a distance of 2 cm. Calculate the linear charge density.

Answer

Electric field produced by the infinite line charges at a distance d having linear charge density λ is given by the relation,

Where,

d = 2 cm = 0.02 m

E = 9 × 10^{4} N/C

∈_{0} = Permittivity of free space

= 9 × 10^{9} N m^{2} C^{−2}

^{}

= 10 μC/m

Therefore, the linear charge density is 10 μC/m.

- 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 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 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 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 12 pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor?

- 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 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:-
In a certain region of space, electric field is along the z-direction throughout. The magnitude of electric field is, however, not constant but increases uniformly along the positive z-direction, at the rate of 10

^{5}NC^{-1 }per metre. What are the force and torque experienced by a system having a total dipole moment equal to 10^{-7}Cm in the negative z-direction? - Q:-
The earth's surface has a negative surface charge density of 10

^{-9}C m^{-2}. The potential difference of 400 kV between the top of the atmosphere and the surface results (due to the low conductivity of the lower atmosphere) in a current of only 1800 A over the entire globe. If there were no mechanism of sustaining atmospheric electric field, how much time (roughly) would be required to neutralise the earth's surface? (This never happens in practice because there is a mechanism to replenish electric charges, namely the continual thunderstorms and lightning in different parts of the globe). (Radius of earth = 6.37 x 10^{6}m.) - Q:-
Two charges

*-q*and*+q*are located at points (0, 0, -*a*) and (0, 0,*a*), respectively.(a) What is the electrostatic potential at the points?

(b) Obtain the dependence of potential on the distance r of a point from the origin when

*r/a*>> 1.(c) How much work is done in moving a small test charge from the point (5, 0, 0) to (-7, 0, 0) along the x-axis? Does the answer change if the path of the test charge between the same points is not along the x-axis?

- Q:-
A 12 pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor?

- Q:-
What is the de Broglie wavelength of a nitrogen molecule in air at 300 K? Assume that the molecule is moving with the root-mean square speed of molecules at this temperature. (Atomic mass of nitrogen = 14.0076 u)

- Q:-
A p-n photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 6000 nm?

- Q:-
The number density of free electrons in a copper conductor estimated in Example 3.1 is 8.5 x 10

^{28}m^{-3}. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is 2.0 x 10^{-6}m^{2}and it is carrying a current of 3.0 A. - Q:- A 100 Ω resistor is connected to a 220 V, 50 Hz ac supply.

(a) What is the rms value of current in the circuit?

(b) What is the net power consumed over a full cycle? - Q:-
The energy flux of sunlight reaching the surface of the earth is 1.388 × 10

^{3}W/m^{2}. How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of 550 nm. - Q:-
In a certain region of space, electric field is along the z-direction throughout. The magnitude of electric field is, however, not constant but increases uniformly along the positive z-direction, at the rate of 105 NC

^{-1 }per metre. What are the force and torque experienced by a system having a total dipole moment equal to 10^{-7}Cm in the negative z-direction?

Rajat Sharma
2019-12-10 09:05:13

Way of solving the question is ok but the calculation is wrong

Jhajj
2019-12-04 19:25:15

Way of solving the problem is correct but calculation is wrong.. otherwise it is correct

anurag misra
2019-09-06 12:13:55

ritesh, answer is wrong if you will convert it in micro coulomb it will become 0.1 micro coulomb per meter

Kundan
2019-08-16 13:09:32

NCERT ans is wrong

physics Nerd
2019-07-26 19:42:18

0.1ÃŽÂ¼C/m

Aman verma
2019-04-30 00:53:22

Answer is 1*10^-7 Coloumb which is 0.1 micro coloumb but your answer is wrong as ncert also printed wrong!!!!!

Amal c Paulson
2019-03-27 07:15:19

Answer is wrong

Arif ahmad
2019-01-03 10:18:36

Answer is wrong

I am right
2018-06-16 14:05:01

Answer is correct 10uC/m = 10 x 10^-6 C/m

Sharan Kumar
2018-05-28 21:55:33

This answer is wrong The correct answer is 1.008ÃƒÂ—10^-6

- NCERT Chapter

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