Phe-07 Assignments 2019 (english).pdf

PHE-07 ASSIGNMENT BOOKLET Bachelor's Degree Programme (B.Sc.) ELECTRIC AND MAGNETIC PHENOMENA Valid from January 1, 2019 to December 31, 2019

It is compulsory to submit the Assignment before filling in the Term-End Examination Form.

Please Note • You can take electives (56 or 64 credits) from a minimum of TWO and a maximum of FOUR science disciplines, viz. Physics, Chemistry, Life Sciences and Mathematics. • You can opt for elective courses worth a MINIMUM OF 8 CREDITS and a MAXIMUM OF 48 CREDITS from any of these four disciplines. • At least 25% of the total credits that you register for in the elective courses from Life Sciences, Chemistry and Physics disciplines must be from the laboratory courses. For example, if you opt for a total of 64 credits of electives in these 3 disciplines, at least 16 credits out of those 64 credits should be from lab courses. • You cannot appear in the Term-End Examination of any course without registering for the course. Otherwise, your result will not be declared and the responsibility will be yours.

School of Sciences Indira Gandhi National Open University Maidan Garhi, New Delhi-110068 2019

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Dear Student, We hope you are familiar with the system of evaluation to be followed for the Bachelor’s Degree Programme. At this stage you may probably like to re-read the Section on assignments in the Programme Guide for Elective Courses that we sent you after your enrolment. A weightage of 30 per cent, as you are aware, has been earmarked for continuous evaluation which would consist of one tutor-marked assignment (TMA) for this course.

Instructions for Formatting Your Assignments Before attempting the assignment, please read the following instructions carefully: 1) On top of the first page of your TMA answer sheet, please write the details exactly in the following format: ENROLMENT NO. : ……………………………………… NAME : ……………………………………… ADDRESS : ……………………………………… ……………………………………… ……………………………………… COURSE CODE

: ……………………………..

COURSE TITLE

: ……………………….…….

ASSIGNMENT NO. : ………………………….… STUDY CENTRE

: ………………………..…….

DATE : ….……………………………...……

Please follow the above format strictly to facilitate evaluation and to avoid delay. 2) Use only foolscap size writing paper (but not of very thin variety) for writing your answers. 3) Leave 4 cm margin on the left, top and bottom of your answer sheet. 4) Your answers should be precise. 5) While solving problems, clearly indicate the question number along with the part being solved. Be precise. Write units at each step of your calculations as done in the text because marks will be deducted for such mistakes. Take care of significant digits in your work. Recheck your work before submitting it. 6) This assignment will remain valid from January 1, 2019 to December 31, 2019. However, you are advised to submit it within 12 weeks of receiving this booklet to accomplish its purpose as a teaching-tool. We strongly feel that you should retain a copy of your assignment response to avoid any unforeseen situation and append, if possible, a photocopy of this booklet with your response. If you have any problems or queries related to the course, you can write to us on the e-mail [email protected] or [email protected] We wish you good luck.

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Tutor Marked Assignment ELECTRIC AND MAGNETIC PHENOMENA Course Code: PHE-07 Assignment Code: PHE-07/TMA/2019 Max. Marks: 100

Note: Attempt all questions. The marks for each question are indicated against it. Symbols have their usual meanings. 1.

Four particles carrying charges + 2q, − 2q, + 4q and − 4q (with q = 1.0 nC) are kept at the vertices of a square of side 6.0 cm. Determine the net electric field due to these charged particles at the centre of the square. What is the electrostatic force on a particle carrying positive charge of 1.0 nC placed at the centre of the square? (8+2)

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The volume charge density of a solid sphere of radius 0.75 m is 0.25 nCm−3. Apply Gauss’s law to calculate the a) electric flux through the sphere and b) electric field at a distance of 1.5 m and at a distance of 0.50 m from the centre of the sphere, respectively. If this sphere were made of conducting material, what would the values of the electric fields be at these distances? (2+3+3+2)

3. a) Three charges q, 2q and q are to be placed on a straight wire of length 10 m. Determine the positions where the charges should to be placed so that the electrostatic potential energy of the system is a minimum. b) Two large parallel conducting plates carrying equal and opposite charges on their surfaces facing each other are placed at a distance of 0.75 m. An electron placed at some point between the plates experiences an electrostatic force of 4.8 × 10-16 N. Calculate the magnitude of the electric field at the position of the electron between the plates. Also determine the potential difference between the plates. 4. a) Explain the mechanism of polarisation in polar and non-polar dielectrics. b) The polarisability of a given material is 1.0×10-40 C2mN−1. Determine its dielectric constant if the number of molecules in 1 m3 volume of the material is 5.0×1025.

(5)

(3+2) (5) (5)

5. a) A parallel plate capacitor is made of two rectangular plates of area 1.0 m2 and the separation between plates is 2.0 mm. A voltage of 100 V is applied across the plates. Calculate the capacitance of the capacitor if a dielectric material of dielectric constant 3.0 is introduced between the plates. What is the charge stored on each plate of the capacitor? (5) b) Determine the effective capacitance of the following combination of capacitors given that the capacitance of each capacitor is 3 μF. (5)

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6. a) The number density of electrons in a metal is 9.64 × 1028 m −3 . What is the drift velocity of electrons in a wire made up of this metal when a current of 4A flows in it given that its cross-sectional area is 2.0 mm2? How long will it take for an electron to travel a distance of 0.10 m in this wire?

(5)

b) Two long, straight, parallel wires 24 cm apart carry currents of I1 = 30A and I2 = 20A in the same direction. Determine the magnetic field in the plane of the two wires at a point halfway between the wires.

(5)

7. a) An electron and a proton, having the same kinetic energy, enter a region of uniform magnetic field moving perpendicular to the field. Calculate the ratio of the radii of their circular paths in the field.

(5)

b) Distinguish between paramagnetic and diamagnetic materials, giving examples.

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8. a) Metallic iron contains approximately 1029 atoms per cubic meter. The magnetic moment of each iron atom is 1.8 × 10−23 Am−1. If all the dipoles were perfectly aligned what would be the magnetisation M and the magnetic moment of a bar 10 cm long and 1cm2 in cross-section? (5) b) Write the plane wave form for the z-component of the electric field vector of an electromagnetic wave of wavelength 10 cm and field strength 200 Vm–1. The wave is propagating in the positive x-direction. (5) 9. Using Maxwell’s equations in free space, derive the wave equation for the z-component of the electric field vector. (10) 10. A uniform plane wave of 10 kHz travelling in free space strikes a large block of a material having ε = 9 ε 0 , μ = 4μ 0 and σ = 0 normal to the surface. If the incident magnetic field vector is given by r B = 10 − 3 sin (ωt − βy ) kˆ tesla Write the complete expressions for the incident, reflected, and transmitted field vectors. (10) ******

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