Electricity and Magnetism (PHYS2239)
BSc, Physics - PHYS
Semester: Second Semester
Level: 200
Year: 2018
REPUBLIC OF CAMEROON THE UNIVERSITY OF BAMENDA
Peace-Work-Fatherland
P. O. BOX 39 Bambili
School/Faculty:SCIENCE Department:_PHYSICS Lecturer(s): MR POTAM AND MR
NGAH-MUTI___
Course Code: _PHYS2239____Course Title: Electricity and magnetism
Date: _13-07-2018_______Halls: __ PBB05________DURATION: 11-14
Instructions: Answer all questions
Section 1: Magnetism
1. A thin infinitely long straight wire carries a current I. Find the B field at some point P which is a
distance R from the wire, using Biot-Savart Law. [2mks]
2. Suppose that there are n turns per unit length of the solenoid in figure 1. Calculate B using Ampere’s
law. Use the rectangular path abcda shown.
Figure 1.
[3 marks]
3. A closed ten turn rectangular loop of wire (5 cm x 10 cm) rotates about an axis with an angular
velocity of 100 (radian)/s. The resistance of the wire is 5 Q. There is a uniform B field perpendicular
to the axis of rotation, with a magnitude of 2 x 10
-2
T.
(a) What is the maximum magnitude of the induced of the induced current?
(b) What is the orientation of the loop at the time of this maximum current?
[2mks]
4. A cylindrical wire of permeability p. carries a steady current I. If the radius of the wire is R, find B
and H inside and outside the wire.
[3mks]
Section 2: Electricity
QUESTION I: ELECTRIC FIELD [6mks]
Consider a charged line of the length L, having a uniform linear charge density placed along the X -
axis of the Cartesian reference frame with its center at the origin.
1. Sketch the diagram showing the electric field at an arbitrary point P (x, y) in the (x, y) plane
created by the element of charge at the element dx’.
2. Express the position vector r’ describing the distance of the point P from the charge element at
the position dx’ and deduce the square of that position.
Express the element of the electric field at P point due to the element dx’,
4. Using questions 1), 2)to deduce the different components of the electric field, E.
5. Calculate those different components in the case where the line charge is infinitely long.
QUESTION II: ELECTRIC POTENTIAL [4mks]
Consider the disk of radius R carrying a uniform charge density cr at a point P at the distance Z (along the
axis of the disk).
www.schoolfaqs.net
1.
Express the element of the potential field at the P point due to one ring of radius r with respect to r, a
and Z.
2.
Deduce the expression of that electric potential at P point.
Good luck!!!
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