MCQs of Principles of Electromechanical Energy Conversion (Electrical Machine - I - 3140913)

Electrical Machine - I (3140913) MCQs

MCQs of Principles of Electromechanical Energy Conversion

Showing 11 to 20 out of 34 Questions

11.

Magnetic stored energy density for iron is given by ______

(a)	$\frac{1}{2} \frac{B}{μ}$
(b)	$\frac{1}{2} B^{2} μ$
(c)	$\frac{1}{2} Φ^{2} R I$
(d)	$\frac{1}{2} \frac{B^{2}}{μ}$

12.

The energy stored in a magnetic field is given by ____________ where L=self-inductance and Rl=reluctance.

(a)	$\frac{1}{2} L I^{2}$
(b)	$\frac{1}{2} \frac{B^{2}}{μ}$
(c)	$\frac{1}{2} Φ R I$
(d)	$\frac{1}{2} Φ^{2} R I$

13.

When a current of 5A flows through a coil of a linear magnetic circuit, it has flux linkages of 2.4 wb-turns. What is the energy stored in the magnetic field of this coil in Joules?

(a)	1.2
(b)	2.4
(c)	6
(d)	24

14.

For a linear electromagnetic circuit, which of the following statement is true?

(a)	Field energy is less than the Co-energy
(b)	Field energy is equal to the Co-energy
(c)	Field energy is greater than the Co-energy
(d)	Co-energy is zero

15.

Consider a magnetic relay with a linear magnetization curve in both of its open and closed position. What happens to the electrical energy input to the relay, when the armature moves slowly from open position to closed position?

(a)	W_elec=W_fld
(b)	W_elec=W_mech
(c)	W_elec=W_mech/2+W_fld/2
(d)	W_elec=0

16.

The electromagnetic torque developed in any physical system, and with magnetic saturation neglected, acts in such a direction as to tend to

(a)	decrease both the reluctance and inductance
(b)	increase both the reluctance and inductance
(c)	decrease the reluctance and increase the inductance
(d)	increase the reluctance and decrease the inductance

17.

Electromagnetic force and/or torque developed in any physical system, acts in such a direction as to tend to ____________

(a)	increase both the field energy and co-energy at a constant current
(b)	increase the field energy and decrease the co-energy at a constant current
(c)	decrease both the field energy and co-energy at a constant current
(d)	decrease the field energy and increase the co-energy at a constant current

18.

Which of the following are examples of doubly-excited magnetic systems?

(a)	Synchronous Machines
(b)	Loudspeakers and Tachometers
(c)	D.C Shunt Machines
(d)	All of the mentioned

19.

Most of the electromagnetic energy conversion devices belong to __________

(a)	singly excited magnetic systems
(b)	doubly excited magnetic systems
(c)	multiply excited magnetic systems
(d)	both doubly excited magnetic systems and multiply excited magnetic systems

20.

In a doubly excited magnetic system with salient pole type stator and rotor, if the rotor is not allowed to move, then the equation for magnetic field stored energy in establishing the currents from zero to I_s and I _r is

(a)	W_fld = 1/2 I_s²Ls+1/2 I_r²Lr
(b)	W_fld =1/2 I_s²Ls+Mrs I_s I_r
(c)	W_fld =1/2 I_s²Ls+1/2 I_r²Lr+ Mrs I_s I_r
(d)	W_fld =1/2 I_r²Ls+Mrs I_s I_r

Showing 11 to 20 out of 34 Questions