Pathak’s Academy Spectrum 2024
Topics: Chapters 10,11,12,13..
Marks: 30 Time: 1h 10 min
Section - A
Q.No. 1 : Select and write the correct answer (any 6) [06]
i) A conducting thick copper rod of length 1 m carries a current of 15 A and is located on the Earth's equator. There the magnetic flux lines of the Earth's magnetic field are horizontal, with the field of 1.3 × 10-4 T, south to north. The magnitude and direction of the force on the rod, when it is oriented so that current flows from west to east, are
(A) 14 × 10-4 N, downward.
(B) 20 × 10-4 N, downward.
(C) 14 × 10-4 N, upward.
(D) 20 × 10-4 N, upward.
ii) A charged particle is in motion having initial velocity v when it enters into a region of uniform magnetic field perpendicular to v. Because of the magnetic force the kinetic energy of the particle will
(A) remain uncharged.(B) get reduced(C) increase. (D) be reduced to zero.
iii) Soft iron is used to make the core of transformer because of its
(A) low coercivity and low retentivity
(B) low coercivity and high retentivity
(C) high coercivity and high retentivity
(D) high coercivity and low retentivity
iv) Which of the following statements is correct for diamagnetic materials?
(A) µr < 1 (B) χ is negative and low
(C) χ does not depend on temperature (D) All of above
v) A circular coil of 100 turns with a cross-sectional area (A) of 1 m 2 is kept with its plane perpendicular to the magnetic field (B) of 1 T. What is the magnetic flux linkage with the coil?
(A) 1 Wb (B) 100 Wb(C) 50 Wb (D) 200 Wb
vi) A current through a coil of self inductance 10 mH increases from 0 to 1 A in 0.1 s. What is the induced emf in the coil?
(A) 0.1 V (B) 1 V (C) 10 V (D) 0.01 V
vii) In an AC circuit, e and i are given by e = 150 sin(150t) V&i = 150 sin(150 t + π/3 ) A. the power dissipated in the circuit is
(A) 106 W (B) 150 W (C) 5625 W (D) Zero
viii) In a series LCR circuit the phase difference between the voltage and the current is 450. Then the power factor will be (A) 0.607 (B) 0.707 (C) 0.808 (D) 1
Q. 2 Answer the following. [04]
i) Which property of soft iron makes it useful for preparing electromagnet?
ii) State Lenz’s law in the light of the principle of conservation of energy.
iii) Calculate the SI unit of Inductance.
iv) Draw the phasor diagram for purely capacitive ckt.
Section - B
Attempt any 5 [5 x 2 = 10 M]
i) Obtain and expression for orbital magnetic moment of an electron rotating
about the nucleus in an atom.
ii) What are eddy currents? State applications of eddy currents
iii) Explain why the inductance of two coils connected in parallel is less than the inductance of either coil.
iv) Discuss the Curie law for paramagnetic material.
iv) What do you mean by electromagnetic induction? State Faraday’s law of induction.
v) Compare between resistance and reactance.
vi) If the rms current in a 50 Hz AC circuit is 5A, the value of the current 1/300 seconds after its value becomes zero is?
Section - C
Attempt any Two. [3 x 2 = 6 M]
i) A toroid of narrow radius of 10 cm has 1000 turns of wire. For a magnetic field
of 5 × 10-2 T along its axis, how much current is required to be passed through
the wire?
ii) Explain Faraday's Laws of Electromagnetic Induction. Deduce equation for EMF
iii) Deduce the average Power equation for LCR ckt with ckt diagram
Section - D
Attempt any One. [1 x 4 = 4 M]
i) Explain Self and Mutual Induction Derive the equation for both with a diagram.
ii) What is Resonance ckt? Deduce the expression for series and parallel resonant circuit with their characteristics .Explain Q factor with the help of diagram.
