If the average coil emf of a DC motor is doubled and flux is halved (keeping other parameters constant) then its shaft speed will become ___________(a) a. Twice of the original speed(b) b. Square of the original speed(c) c. Four times of the original speed(d) d. Half of the original speedThe question was asked during an online interview.My question is based upon EMF and Torque Production in section Circuit Model, Emf and Torque of DC Machines

If the average coil emf of a DC motor is doubled and flux is halved (k

1.	If the average coil emf of a DC motor is doubled and flux is halved (keeping other parameters constant) then its shaft speed will become ___________(a) a. Twice of the original speed(b) b. Square of the original speed(c) c. Four times of the original speed(d) d. Half of the original speedThe question was asked during an online interview.My question is based upon EMF and Torque Production in section Circuit Model, Emf and Torque of DC Machines
Answer» The correct option is (c) c. Four times of the original speed The BEST explanation: Induced emf in a DC MACHINE is equal to, From the emf equation we GET speed of the shaft i.e. n α E/Z, when all other parameters are kept constant. So, when E is doubled n becomes twice the original, HALVING flux on reduced emf will QUADRUPLED the speed of a DC machine.

Discussion

No Comment Found

Related InterviewSolutions

What is the armature current for a DC motor if terminal voltage is 255V and open circuit voltage is equal to 250V, where armature resistance is 0.05Ω?(a) 10A(b) 100A(c) 1KA(d) 1AThis question was posed to me in my homework.Query is from Electromagnetic Power and Circuit Models in section Circuit Model, Emf and Torque of DC Machines
When torque of the electromagnetic origin is in the direction of rotation of armature, machine is said to be operating in which of the following mode?(a) Depends on other parameters(b) Generating(c) Motoring(d) InducingI had been asked this question by my college director while I was bunking the class.This question is from Electromagnetic Power and Circuit Models in chapter Circuit Model, Emf and Torque of DC Machines
What is the armature current for a DC generator if terminal voltage is observed to be 245V and open circuit voltage is equal to 250V, where armature resistance is 0.05Ω?(a) 10A(b) 100A(c) 1KA(d) 1AThis question was posed to me by my college professor while I was bunking the class.Question is taken from Electromagnetic Power and Circuit Models topic in division Circuit Model, Emf and Torque of DC Machines
For a DC generator feeding 100kW power into 230V mains, having armature resistance and field resistance equal to 0.08Ω and 115Ω resp. The value of armature current is_____(a) 436.8 A(b) 434.8 a(c) 432.8 A(d) Data insufficientThe question was asked in an online interview.This is a very interesting question from Electromagnetic Power and Circuit Models topic in section Circuit Model, Emf and Torque of DC Machines
When torque of the electromagnetic origin is in the opposite direction of rotation of armature, machine is said to be operating in which of the following mode?(a) Depends on other parameters(b) Generating(c) Motoring(d) InducingThe question was posed to me by my school teacher while I was bunking the class.This key question is from Electromagnetic Power and Circuit Models topic in portion Circuit Model, Emf and Torque of DC Machines
Simple equation of DC machine operating in generating mode, with non-zero Ra value is________(a) Vt = Ea – Ia/Ra(b) Vt = Ea + Ia*Ra(c) Vt = – Ea + Ia*Ra(d) Vt = Ea – Ia*RaI have been asked this question in an internship interview.This intriguing question originated from Electromagnetic Power and Circuit Models in division Circuit Model, Emf and Torque of DC Machines
When Ea
Product of torque and mechanical angular velocity ω is_____(a) Ea/ω(b) Ea*Ia(c) ω/Ea(d) Can’t tellI had been asked this question at a job interview.My doubt stems from Electromagnetic Power and Circuit Models topic in portion Circuit Model, Emf and Torque of DC Machines
For an ideal DC machine, which phenomenon will reduce the terminal voltage?(a) Armature reaction(b) Commutation(c) Armature ohmic losses(d) All will contribute in reducing the terminal voltageI have been asked this question in quiz.Origin of the question is EMF and Torque Production topic in division Circuit Model, Emf and Torque of DC Machines
In a DC machine, what is the torque induced beyond the pole shoes?(a) 0(b) 2/π *∅*i(c) π *∅*i/2(d) Can’t be calculatedThe question was posed to me during an internship interview.I want to ask this question from EMF and Torque Production in division Circuit Model, Emf and Torque of DC Machines

Discussion

No Comment Found

Related InterviewSolutions

Reply to Comment