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Phys 220: Electricity And Magnetism Ii Question Paper
Phys 220: Electricity And Magnetism Ii
Course:Bachelor Of Computer Science
Institution: Chuka University question papers
Exam Year:2013
CHUKA
UNIVERSITY
UNIVERSITY EXAMINATIONS
SECOND YEAR EXAMINATION FOR THE AWARD OF DEGREE OF
BACHELOR OF EDUCATION (SCIENCE) AND
BACHELOR OF SCIENCE (COMPUTER SCIENCE)
PHYS 220: ELECTRICITY AND MAGNETISM II
STREAMS: B.ED (SCI), B.Sc. (COMP SCI) Y2S2 TIME: 2 HOURS
DAY/DATE: TUESDAY 13/8/2013 8.30 A.M. – 10.30 A.M.
INSTRUCTIONS:
Answer question ONE (Compulsory) and ANY other two questions.
Useful constants:
Permeability of free space, µ=4p x ?10?^(-7)H/M
Permittivity of free space, e_o=8.854 ×?10?^(-12)F/M
Stoke’s theorem: ?¦?A ?.dl ?=?_s¦?? ?×A ?.ds??
Question One (30 Marks)
Radio waves and gamma rays are examples of electromagnetic waves. How are they detected? [2 marks]
State one source of sinusoidal wave form in the laboratory. [1 mark]
State and explain the integral form of Gauss’s law. [2 marks]
Given a sphere of radius R enclosing a charge q at its centre, use Gauss law to determine the electric flux over the spherical surface. [5 marks]
Define an electric dipole and give an example of a naturally occurring electric dipole.
[2 marks]
Using a well labeled diagram, describe how a dielectric material respond when subjected to electric field. State how it affect the capacitance of a parallel plate capacitor.
[5 marks]
From permeability and permittivity of free space, calculate the velocity of an electromagnetic wave. [2 marks]
An LCR series circuit was connected across a 12V, 50H2 power supply. The current in the circuit is 0.05A and differs in phase with the p.d applied by 60o.
(i) Sketch the vector diagram of the problem. [2 marks]
(ii) Determine the values of R and L. [4 marks]
(iii) Determine the value of the capacitor which when connected in series
in the circuit will bring the current into phase with the applied p.d [3 marks]
Define the following terms as applied to transmission lines.
(i) Characteristic impedance
(ii) Propagation velocity [2 marks]
Question 2 (20 Marks)
Gaussian surface S' of radius ,r, is drawn inside a sphere of radius R enclosing a charge Q as sown in figure 1.
Show using Gauss law that electric field on the surface of the Gaussian Surface S1 is given by
E ?=1/?4pe?_o Q/R^3 ·r
[7 marks]
Since ? ?·B ?=0, then if the surface integral is not closed, magnetic flux that changes with time is obtained which produces an emf that is a non-conservating circulating electric field with a non zero closed line integral. Use this statement with Stokes theorem to derive Maxwell’s third equation of electromagnetism. [10 marks]
State Maxwell’s equations of electromagnetism in a vacuum. [3 marks]
Question 3 (20 Marks)
A pair of equal and opposite point charges separated by a vector distance ,d, is shown in figure 2.
Fig. 2: Electric dipole
The vector s ? moves from the negative to the positive charge and is along the axis of the pair.
Determine the electric field at point P, at distance r1 from the centre of the dipole and parallel to the axis. [12 marks]
Given an infinite sheet of charge with uniform surface charge density s and area A, use Gauss law to determine the electric flux due to these charges. [8 marks]
Question 4 (20 Marks)
An LRC series circuit is connected to an ac source of voltage 150 sin1000t. if R = 400?, L = 0.9H and C = 2.1µF, calculate the;
(i) impedance of the circuit [3 marks]
(ii) peak current [2 marks]
(iii) phase angle [3 marks]
(iv) average power dissipated [2 marks]
(v) resonance frequency [2 marks]
An hemisphere of radius R enclose a charge -2q at its centre. Determine the flux on its surface. [8 marks]
Question 5 (20 Marks)
What are the functions of the following:
(i) Transformer
(ii) Delay line
(iii) Transmission lines
(iv) Filters [4 marks]
Sketch the general circuit of a transmission line and state its general characteristics.
[5 marks]
For ideal (lossless) transmission line, what characteristics are assumed and how will its circuit behave. [2 marks]
Illustrate using a simple diagram the following transmission lines:
(i) Terminated
(ii) Short circuit
(iii) Open circuit [3 marks]
Show that the electric field due to infinite line of charges with line charge density ?
is given by,
E=?/(2pe_o r)
Where r is the radius of Gaussian surface? [6 marks]
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