This page offers a step-by-step solution to the specific question **NCERT Class 12th Physics - Electric Charges and Field | an infinite line charge produces a field of 9 tim Answer ** from NCERT Class 12th Physics, Chapter Electric Charges and Field.

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 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 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:-
The electrostatic force on a small sphere of charge 0.4 μC due to another small sphere of charge − 0.8 μC in air is 0.2 N.

(a) What is the distance between the two spheres?

(b) What is the force on the second sphere due to the first?

- Q:-
Two point charges q

_{A}= 3 μC and q_{B}= −3 μC are located 20 cm apart in vacuum.(a) What is the electric field at the midpoint O of the line AB joining the two charges?

(b) If a negative test charge of magnitude 1.5 × 10

^{−9}C is placed at this point, what is the force experienced by the test charge? - 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:-
A uniformly charged conducting sphere of 2.4 m diameter has a surface charge density of 80.0 μC/m

^{2}.(a) Find the charge on the sphere.

(b) What is the total electric flux leaving the surface of the sphere?

- Q:-
Suppose the spheres A and B in Exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?

- Q:-
Answer the following questions regarding earth's magnetism:

(a) A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth's magnetic field.

(b) The angle of dip at a location in southern India is about 18º.

Would you expect a greater or smaller dip angle in Britain?

(c) If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?

(d) In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?

(e) The earth's field, it is claimed, roughly approximates the field due to a dipole of magnetic moment 8 x 1022 J T

^{-1 }located at its centre. Check the order of magnitude of this number in some way.(f ) Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth's surface oriented in different directions. How is such a thing possible at all?

- Q:-
(a) Two stable isotopes of lithium 6Li3 and7Li3 have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.

(b) Boron has two stable isotopes,

^{10}B_{5}and^{11}B_{5}. Their respective masses are 10.01294 u and 11.00931 u, and the atomic mass of boron is 10.811 u. Find the abundances of^{10}B_{5}and^{11}B_{5}. - Q:-
A small candle, 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of curvature 36 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would the screen have to be moved?

- Q:-
Figure 8.6 shows a capacitor made of two circular plates each of radius 12 cm, and separated by 5.0 cm. The capacitor is being charged by an external source (not shown in the figure). The charging current is constant and equal to 0.15 A.

(a) Calculate the capacitance and the rate of charge of potential difference between the plates.

(b) Obtain the displacement current across the plates.

(c) Is Kirchhoff’s first rule (junction rule) valid at each plate of the capacitor? Explain.

- Q:- The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4Ω, what is the maximum current that can be drawn from the battery?
- 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 rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s−1 in a direction normal to the

(a) longer side,

(b) shorter side of the loop? For how long does the induced voltage last in each case? - 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:-
Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of

(a) reflected, and

(b) refracted light? Refractive index of water is 1.33. - Q:-
Two charges 5 x 10

^{-8}C and -3 x 10^{-8}C are located 16 cm apart. At what point(s) on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.

- Q:-

Obtain the equivalent capacitance of the network in below Figure. For a 300 V supply, determine the charge and voltage across each capacitor. - Q:-
Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of

(a) reflected, and

(b) refracted light? Refractive index of water is 1.33. - Q:-
A storage battery of emf 8.0 V and internal resistance 0.5 Ω is being charged by a 120 V dc supply using a series resistor of 15.5 Ω. What is the terminal voltage of the battery during charging? What is the purpose of having a series resistor in the charging circuit?

- Q:-
A short bar magnet placed with its axis at 30º with a uniform externalmagnetic field of 0.25 T experiences a torque of magnitude equal to 4.5 x 10

^{-2}J. What is the magnitude of magnetic moment of the magnet? - Q:-
What is the de Broglie wavelength of

(a) a bullet of mass 0.040 kg travelling at the speed of 1.0 km/s,

(b) a ball of mass 0.060 kg moving at a speed of 1.0 m/s, and

(c) a dust particle of mass 1.0 × 10

^{−9}kg drifting with a speed of 2.2 m/s? - Q:-
Two moving coil meters, M

_{1}and M_{2}have the following particulars:R

_{1}= 10 Ω, N_{1}= 30,A

_{1 }= 3.6 x 10^{-3}m2, B1 = 0.25 TR

_{2}= 14 Ω, N_{2}= 42,A

_{2}= 1.8 x 10-3 m2, B_{2}= 0.50 T(The spring constants are identical for the two meters).

Determine the ratio of (a) current sensitivity and (b) voltage sensitivity of M

_{2}and M_{1}. - Q:-
The magnetic moment vectors

**μ**and_{s}**μ**associated with the intrinsic spin angular momentum_{l}**S**and orbital angular momentum**l,**respectively, of an electron are predicted by quantum theory (and verified experimentally to a high accuracy) to be given by:**μ**= -(_{s}*e*/*m*)**S**,**μ**= -(_{l}*e*/2*m*)**l**Which of these relations is in accordance with the result expected classically?

Outline the derivation of the classical result.

- Q:-
Determine the current drawn from a 12 V supply with internal resistance 0.5 Ω by the infinite network shown in Fig. 3.32. Each resistor has 1 Ω resistance.

- Q:-
A negligibly small current is passed through a wire of length 15 m and uniform cross-section 6.0 x 10

^{-7}m^{2}, and its resistance is measured to be 5.0 Ω. What is the resistivity of the material at the temperature of the experiment? - Q:-
Estimate the distance for which ray optics is good approximation for an aperture of 4 mm and wavelength 400 nm.

Kundan
2019-08-16 13:09:32

NCERT ans is wrong

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

0.1Î¼C/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 1.008Ã10^-6

Sapna
2018-05-26 03:11:26

Really helpful

Ritesh
2018-05-25 18:34:30

Sister answere sahi hi apne answeres ko micro coulomb me badalo

sweety priya
2017-08-21 09:51:46

hi your answer is wrong the correct answer is 10^-7. explanation :- ð¸ = ð /2ðð0ð â ð = 2ðð0ðð¸ ð=2*3.14*8.85*10^-12*9*10^4 ð=6.28*18*10^-2*10^4*8.85*10^-12 ð=1000.3*10^2*10^-12 ð=10^3*10^2*10^-12 ð=10^-7 so,the correct answer is 10^-7

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