DFCCIL’21 EE: Daily Practices Quiz 15-July-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 08 min.

Q1. The capacitor used in single-phase capacitor motors have no
(a) Voltage rating
(b) Dielectric medium
(c) Polarity marking
(d) Definite value

Q2. The approximate efficiency of a 3-phase, 50 Hz, 4-pole induction motor running at 1350 rpm is….
(a) 90 %
(b) 65 %
(c) 40 %
(d) None of the above

Q3. In the depletion region of a PN junction, there is a shortage of
(a) Donor ions
(b) Acceptor’s ions
(c) Holes and electrons
(d) None of the above

Q4. A PN junction acts as a……….
(a) Unidirectional switch
(b) Bidirectional switch
(c) Controlled switch
(d) None of the above

Q5. The rotor of which motor does not have winding on it?
(a) Repulsion motor
(b) Universal motor
(c) Reluctance motor
(d) Hysteresis motor

Q6. The torque-slip characteristics of a polyphase induction motor becomes almost linear at small value of slip, because in this region of slips:
(a) The effective rotor resistance is very large compared to the rotor reactance.
(b) The effective rotor resistance is very small compared to the rotor reactance.
(c) The effective rotor resistance is equal to the rotor reactance.
(d) The effective rotor resistance is equal to the stator reactance.

SOLUTIONS
S1. Ans.(c)
Sol. The capacitor used in single-phase capacitor motors have no polarity marking.
The capacitor used is electrolytic and in series with an auxiliary winding for starting.
An electrolytic capacitor has no polarity marking.

S2. Ans.(a)
Sol. For 3-phase induction motor: efficiency=(1-s)=N/N_s
Where, s=slip
N= rotor speed
And N_s=synchronous speed
ACQ: N_s=(120 f)/P=(120×50)/4=1500 rpm
∴ efficiency=(1-s)=N_r/N_s =1350/1500×100=90 %

S3. Ans.(c)
Sol. Due to diffusion across the PN junction during its formation, the charge carries (free electrons and holes) are absent in the depletion region.
Depletion region of a p-n junction is formed due to the shortage of holes and electrons.

S4. Ans.(a)
Sol. A PN junction conducts current only when forward biased while no current conduction takes place when reversed biased. Therefore, a PN junction behaves as UNIDIRECTIONAL switch.

S5. Ans.(d)
Sol. A Hysteresis Motor is a synchronous motor with a uniform air gap and without DC excitation.
The rotor of the motor is made up of smooth chrome steel cylinder and it has no winding.

S6. Ans.(a)
Sol. The torque-slip characteristics of a polyphase induction motor becomes almost linear at small value of slip, i.e., X_2/R_2 ≪1.

×

Download success!

Thanks for downloading the guide. For similar guides, free study material, quizzes, videos and job alerts you can download the Adda247 app from play store.

[adda247_lead_form]

Leave a comment

Your email address will not be published. Required fields are marked *

Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Login

OR

Forgot Password?

Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Sign Up

OR
Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Forgot Password

Enter the email address associated with your account, and we'll email you an OTP to verify it's you.


Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Enter OTP

Please enter the OTP sent to
/6


Did not recive OTP?

Resend in 60s

Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Change Password



Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Almost there

Please enter your phone no. to proceed
+91

Join India's largest learning destination

What You Will get ?

  • Job Alerts
  • Daily Quizzes
  • Subject-Wise Quizzes
  • Current Affairs
  • Previous year question papers
  • Doubt Solving session

Enter OTP

Please enter the OTP sent to Edit Number


Did not recive OTP?

Resend 60

By skipping this step you will not recieve any free content avalaible on adda247, also you will miss onto notification and job alerts

Are you sure you want to skip this step?

By skipping this step you will not recieve any free content avalaible on adda247, also you will miss onto notification and job alerts

Are you sure you want to skip this step?