Dharmsinh Desai University 2009 B.E Tutorial - Question Paper

Tutorial -1
B.E. Sem: one (ALL)
SUB: Basic Electrical Engg.

Q-1 Fill in the blanks:

1.Reluctance in magnetic circuit is equivalent to ______ in electical circuit.
2.Unit of magnetic flux density is _______. (wb, wb/m, wb/sq.m)
3.Permeability of free space is ________.
4.Mmf per unit length is called ________.
5.Flux which does not follow desired path in a magnetic field is known as _____.
6.If area of cross part of a solenoid is a then S = _______.
7.1 Wb = _______ magnetic lines.

Q-2 ans the subsequent questions:

1.Why relative permeability of air is 1?
2.Define magnetic leakage.
3.What is leakage co-efficient?
4.Explain the effect of fringing effect.
5.State the KCL and KVL of magnetic circuit with equestion.

Q-3 Solve the examples:

1.An iron ring 15 cm in diameter, and 10 sq. cm in c.s. Is wound with 200 turns of wire. For a flux
density of one wb/sq. m, and a permiabilityof 500, obtain the exciting current.
2.An iron ring made of 3 parts has l1 = 10 cm, A1= five sq.cm. i2=8cm, A2 = three sq.cm, l3 = 6cm
and A3 = 2.5.sq.cm. It is wound with a ciol of 250 turns. compute the requuired to produce a
flux of 0.4 mwb in the ring. M1 = 2670, M2 = 1050, M3 = 650.
3.An iron ring 100 cm mean diameter, and 10 sq cm cross part has 1000 turns of copper wire
wound on it. If the permiability of the materialis 1500, and it is needed to produce a flux density
of one Wb/sq.m.in an air gap of two mm width in the ring, find(1)reluctance of ring; (2)flux required,
(3) mmf needed (4) current produced. Neglect leakage and fringing.
4.(a) iron ring wound with 500 turns solenoid produces a flux density 0.94 tesla in the ring carrying
a current pf 2.4 amps. The mean length of iron path is 80 cm, and that of an air gap is 1mm.
Determine relative permiabilityof iron.(b) Determine the coefficient of self inductaance, and
energy stored in the above arraangement, if the area of cross-section is 20 sq cm.
5.An eletromagnet of form shwon beneath is excited by 2 coils, every having 500 turns. When the
exciting current is 0.8 A, and the resulatant flux density provide permiabilityof 1250, compute (1)
tltal reluctance (2) flux produced 0.5 cm airgap.
6.A magnetic coe made up of an alloy has the dimensions as shown in fig. compute the exciting
current needed to produce a flux of one mWb in the airgap. Neglect leakage, and fringing. B/H
curve is as follows.

B(Tesla) 1 1.2 1.42 1.5125 1.6
H(AT/m) 200 400 1791.4 3300 6000

Earning:   Approval pending.