QUIZ1-EM1

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

• 1/2 Li2

• 1/2 (mmf*Rl)2

• 1/2∅Rl

• 1/2 φ2i

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

• Field energy is less than the Co-energy

• Field energy is equal to the Co-energy

• Field energy is greater than the Co-energy

• Co-energy is zero

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

• Synchronous Machines

• Loudspeakers and Tachometers

• D.C Shunt Machines

• All of the mentioned

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 is and ir is __________

• Wfld=1/2 is2Ls+1/2 ir2Lr

• Wfld=1/2 is2Ls+Mrs is ir

• Wfld=1/2 is2Ls+1/2 ir2Lr+Mrs is ir

• Wfld=1/2 ir2Lr+Mrs is ir

In a doubly excited magnetic system of salient pole type stator and rotor, the reluctance torque is present only when _____________

• both stator and rotor currents are acting

• stator current is acting alone

• rotor current is acting alone

• any of the stator or rotor currents acting alone

Which component of torque in the following equation is called the electromagnetic torque of electromagnetic energy conversion device?

• Te=1/2is2dLs/dθr+1/2ir2dLr/dθr+isirdMsr/dθr

• 1/2is2dLs/dθr

• 1/2ir2dLr/dθr

• isirdMsr/dθr

• all of the mentioned

Which of the following statements are true about electromagnetic torques and reluctance torques?

• (i) electromagnetic torque can exist only if both windings carry current (ii) reluctance torque depends on the direction of current in stator or rotor windings (iii) reluctance torque doesn't depend on the direction of current in stator or rotor windings (iv) electromagnetic torque depend on the direction of currents is and ir (v) electromagnetic torque doesn't depend on the direction of currents is and ir

• (i), (ii), (iii)

• (ii), (iii), (v)

• (i), (iii), (iv)

• (ii), (iii), (iv)

Direction of induced emf is determined by __________

• Fleming’s left hand rule

• Fleming’s right hand rule

• Faraday’s law

• Right hand thumb rule

“The direction of an induced e.m.f. is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that e.m.f.”, this is the statement for?

• Fleming’s left hand rule

• Fleming’s right hand rule

• Faraday’s law

• Lenz’s law

The equivalent of the current I in magnetic ohm’s law is?

• Flux

• Reluctance

• MMF

• Resistance