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Asked/Added Questions From NCERT:


Question 1. Asked on :18 August 2020:05:41:09 PM

Give the SI unit of inductive reactance?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
ohmΩ.

-Answered by Shruti Srivastva On 18 August 2020:05:43:13 PM


Question 2. Asked on :18 August 2020:05:37:19 PM

The instantaneous current and voltage of an a.c. circuit are given by 


i = 10 sin 314t A and V = 50 sin 314 t V.


What is the power dissipation in the circuit?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

Pav = v0i02 

cos Φ= 50 X 102 

cos 0º = 250 W.

-Answered by Shruti Srivastva On 18 August 2020:05:39:28 PM


Question 3. Asked on :18 August 2020:05:33:17 PM

Give expression for the average value of the a.c. voltage V = VO sin ωt over the time interval t = 0 and t = π
ω
 .

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

Vav = 2π
 V0  = 0.637 V0.

-Answered by Shruti Srivastva On 18 August 2020:05:35:54 PM


Question 4. Asked on :18 August 2020:05:29:44 PM

The power factor of an a.c. circuit is 0.5. What will be the phase difference between voltage and current in this circuit?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

Power factor = cosΦ = 0.5

Phase difference,Φ = 60º.

-Answered by Shruti Srivastva On 18 August 2020:05:31:36 PM


Question 5. Asked on :18 August 2020:05:28:08 PM

How can iron loss in a transformer be reduced? 

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
It can be reduced by using a laminated core in the transformer. 

-Answered by Shruti Srivastva On 18 August 2020:05:29:00 PM


Question 6. Asked on :18 August 2020:05:26:07 PM

What is iron loss in a transformer?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Due to the production of eddy currents in the iron core of a transformer, some electrical energy is wasted as heat. This energy loss is called iron loss. 

-Answered by Shruti Srivastva On 18 August 2020:05:26:40 PM


Question 7. Asked on :18 August 2020:05:23:33 PM

What is copper loss in a transformer?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Due to the resistance of primary and secondary windings of a transformer, some electrical energy is wasted as heat. The energy loss is called copper loss. 

-Answered by Shruti Srivastva On 18 August 2020:05:24:15 PM


Question 8. Asked on :18 August 2020:05:22:13 PM

Can we use transformer to set up d.c. voltage?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
No. 

-Answered by Shruti Srivastva On 18 August 2020:05:23:21 PM


Question 9. Asked on :18 August 2020:05:20:56 PM

Which device will you use to set up a.c. voltage?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Transformer.

-Answered by Shruti Srivastva On 18 August 2020:05:22:01 PM


Question 10. Asked on :18 August 2020:05:19:17 PM

Give two reasons for power loss in a transformer?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
(i) Magnetic flux leakage. 

(ii) Hysteresis loss.

-Answered by Shruti Srivastva On 18 August 2020:05:20:08 PM


Question 11. Asked on :18 August 2020:05:16:56 PM

State the principle of the transformer?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
It works on the principle of mutual induction i.e., when a charging current is passed through one coil, an induced emf is set up in the neighbouring coil.

-Answered by Shruti Srivastva On 18 August 2020:05:17:35 PM


Question 12. Asked on :18 August 2020:05:15:18 PM

How can an a.c. generator be converted into d.c. generator?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
By replacing slip rings by split ring commutator.

-Answered by Shruti Srivastva On 18 August 2020:05:16:10 PM


Question 13. Asked on :18 August 2020:05:14:26 PM

State the principles of a.c. generator?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Rohit Rajput
AC generators work on the principle of Faraday's law of electromagnetic induction which states that electromotive force -EMF or voltage – is generated in a current-carrying conductor that cuts a uniform magnetic field.

-Answered by Rohit Rajput On 26 September 2020:07:25:09 PM


Question 14. Asked on :17 August 2020:06:25:11 PM

What is direct current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Anjali Kumari
 flow of electricity that goes in one direction only

-Answered by Anjali Kumari On 12 October 2020:07:45:14 PM


Question 15. Asked on :17 August 2020:06:24:12 PM

What is alternating current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Anjali Kumari
a flow of electricity that changes direction regularly many times a second

-Answered by Anjali Kumari On 12 October 2020:07:46:14 PM


Question 16. Asked on :17 August 2020:06:16:10 PM

Where does the energy reside in an inductor when a current I0 is established in it?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The energy reside in the magnetif field of the inductor coil?

-Answered by Shruti Srivastva On 17 August 2020:06:17:37 PM


Question 17. Asked on :17 August 2020:06:14:38 PM

Where does the energy reside in a charged capacitor?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The energy resides in the electric field between the plates of a charged capacitor.

-Answered by Shruti Srivastva On 17 August 2020:06:15:11 PM


Question 18. Asked on :17 August 2020:06:12:19 PM

In pure LC circuit, what is the energy stored when peak current is I0?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

Total energy stored= 12 LI02.

-Answered by Shruti Srivastva On 17 August 2020:06:13:31 PM


Question 19. Asked on :17 August 2020:06:11:12 PM

What are the dimensions of √LC?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
{M0L0T1}

-Answered by Shruti Srivastva On 17 August 2020:06:11:57 PM


Question 20. Asked on :17 August 2020:06:08:38 PM

What is the natural frequency of LC circuit?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

                                   

The natural frequency of LC circuit

F= 12π√LC 

-Answered by Shruti Srivastva On 17 August 2020:06:09:35 PM


Question 21. Asked on :17 August 2020:06:07:19 PM

Is the direction of current during the discharging of capacitor same as that during the charging process?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
No.

-Answered by Shruti Srivastva On 17 August 2020:06:08:25 PM


Question 22. Asked on :17 August 2020:06:06:26 PM

What are units of product RC?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Second.

-Answered by Shruti Srivastva On 17 August 2020:06:06:58 PM


Question 23. Asked on :17 August 2020:06:05:05 PM

What are dimensions of product RC?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
M0L0T1

-Answered by Shruti Srivastva On 17 August 2020:06:05:51 PM


Question 24. Asked on :17 August 2020:06:03:37 PM

How can we improve the Q-factor o a series resonance current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
By decreasing R or C or by increasing L.

-Answered by Shruti Srivastva On 17 August 2020:06:04:26 PM


Question 25. Asked on :17 August 2020:06:01:51 PM

What is the function of a choke coil in a flurescent tube?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
A choke coil reduces current without wasting electrical energy in the form of heat.

-Answered by Shruti Srivastva On 17 August 2020:06:02:46 PM


Question 26. Asked on :17 August 2020:05:59:08 PM

In a serie LCR circuit, VL = VC = VR. What is the value of power factor?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Power factor, cos Φ = 1

-Answered by Shruti Srivastva On 17 August 2020:06:00:42 PM


Question 27. Asked on :17 August 2020:05:57:21 PM

What are the factors on which the power factor?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
It depends on the value of L and R and the frequency o a.c. sourece.

-Answered by Shruti Srivastva On 17 August 2020:05:57:59 PM


Question 28. Asked on :17 August 2020:05:54:36 PM

What is the significance of the Q-factor in an a.c. circuit?

-Added by Shruti Srivastva Physical Education » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The quality factor-Q gives a measure of the sharpness of current peak in the resonance condition of the LCR - circuit.

-Answered by Shruti Srivastva On 17 August 2020:05:55:56 PM


Question 29. Asked on :17 August 2020:05:52:13 PM

A series LCR circuit is connected to an a.c.c source. In which of its part power dissipation occurs- L,C or R? 

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Ressistance R. 

-Answered by Shruti Srivastva On 17 August 2020:05:54:10 PM


Question 30. Asked on :17 August 2020:05:35:06 PM

What is wattless current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The current in an a.c. circuit is wattless if the average power consumed in the circuit is zero.

-Answered by Shruti Srivastva On 17 August 2020:05:35:52 PM


Question 31. Asked on :17 August 2020:05:31:15 PM

What is the power factor of an LCR series circuit at resonance?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
At resonance, Z = R.

 power factor, cos Φ= RZ 

                              = RR  = 1  

-Answered by Shruti Srivastva On 17 August 2020:05:32:43 PM


Question 32. Asked on :17 August 2020:05:29:34 PM

What are the maximum and minimum values of power factor of a.c. circuit?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Maximum = 1

Minimum = 0

-Answered by Shruti Srivastva On 17 August 2020:05:30:41 PM


Question 33. Asked on :17 August 2020:05:27:34 PM

Define power factor. 

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The power actor is defined as the ratio of true power to the apparent power of an a.c. current.

-Answered by Shruti Srivastva On 17 August 2020:05:28:33 PM


Question 34. Asked on :17 August 2020:05:25:49 PM

What is meant by admittance of an a.c. current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The reciprocal of the impedance of an a.c. circuit is called its admittance. 

-Answered by Shruti Srivastva On 17 August 2020:05:26:45 PM


Question 35. Asked on :17 August 2020:05:23:31 PM

When does a series LCR-circuit have minimum impedance?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
At resotance,  when XL XC.

-Answered by Shruti Srivastva On 17 August 2020:05:24:28 PM


Question 36. Asked on :17 August 2020:05:21:18 PM

What is impedance?

-Added by Shruti Srivastva Physical Education » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The total opposition to the flow of current due to resistance R as well as recatnce X in a circuit is called impedance. It is given by Z = √R2 + X

-Answered by Shruti Srivastva On 17 August 2020:05:21:45 PM


Question 37. Asked on :17 August 2020:05:17:39 PM

What is the capacitive reactance of a capacitor used in a circuit having d.c. emf?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
For d.c., f = 0,

 so, X= 12π f C = 

-Answered by Shruti Srivastva On 17 August 2020:05:19:19 PM


Question 38. Asked on :15 August 2020:05:46:11 PM

Give the phase difference between the appied a.c. voltage and the circuit in an LCR circuit at resonance. 

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

zero. 

-Answered by Shruti Srivastva On 15 August 2020:05:47:37 PM


Question 39. Asked on :15 August 2020:05:42:24 PM

What is the phase differnce between the voltage across L and C in a series LCR circuit connected to an a.c. source?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
180° and π radian. 

-Answered by Shruti Srivastva On 15 August 2020:05:43:55 PM


Question 40. Asked on :15 August 2020:05:39:45 PM

What is phase relationship between current and en in an a.c. circuit containing a capacitor only?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
In a capacitor a.c. circuit leads the emf in phase by π/2 radian. 

-Answered by Shruti Srivastva On 15 August 2020:05:41:21 PM


Question 41. Asked on :15 August 2020:05:36:26 PM

What is the phase relationship between current and voltage in an inductor?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

In an inductor, the current lage behind the voltage by a phase angle of π/2 rad.

-Answered by Shruti Srivastva On 15 August 2020:05:38:16 PM


Question 42. Asked on :15 August 2020:05:34:25 PM

What is the reactance of a capacitor of capacitance C at  hertz?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

Xc = 12π f C .

-Answered by Shruti Srivastva On 15 August 2020:05:35:33 PM


Question 43. Asked on :15 August 2020:05:32:52 PM

Write the SI unit of 1 / ωC ?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
ohm Ω.

-Answered by Shruti Srivastva On 15 August 2020:05:33:59 PM


Question 44. Asked on :15 August 2020:05:31:11 PM

How does the inductive reactance depend on of a.c.?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Directly.

-Answered by Shruti Srivastva On 15 August 2020:05:32:32 PM


Question 45. Asked on :15 August 2020:05:28:12 PM

How does the capacitive reactance depends on frequency of a.c.?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

Capacitive reactance varies inversely with frequncy of a.c.

-Answered by Shruti Srivastva On 15 August 2020:05:29:17 PM


Question 46. Asked on :15 August 2020:05:27:28 PM

Write the SI unit of capacitive reactance.

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
ohm Ω.

-Answered by Shruti Srivastva On 15 August 2020:05:27:56 PM


Question 47. Asked on :15 August 2020:05:25:21 PM

Define capacitive reactance. 

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The capacitive reactance of a capacitor is the elective resistance offered by it to the flow of current through it.

-Answered by Shruti Srivastva On 15 August 2020:05:26:04 PM


Question 48. Asked on :15 August 2020:05:24:12 PM

Write the SI unit of inductive reactance?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
ohm Ω.

-Answered by Shruti Srivastva On 15 August 2020:05:24:59 PM


Question 49. Asked on :15 August 2020:05:20:44 PM

Define inductive reactance?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
The inductive reactance of an inductor is the elective resistance offered by it to the flow of current through it. 

-Answered by Shruti Srivastva On 15 August 2020:05:21:56 PM


Question 50. Asked on :15 August 2020:05:20:02 PM

What is form factor?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

It is the ratio of the arms value of a.c. to its average value.

-Answered by Shruti Srivastva On 15 August 2020:05:23:24 PM


Question 51. Asked on :15 August 2020:05:16:38 PM

Define the root mean square value of an alternating current.

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
It is the value of d.c. which produces the same heating effect in a given resitor as is produced by the given alternating current when passed for the same time.

-Answered by Shruti Srivastva On 15 August 2020:05:17:54 PM


Question 52. Asked on :15 August 2020:05:15:36 PM

Write the full form of RMS?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Root Mean Square.

-Answered by Shruti Srivastva On 15 August 2020:05:16:11 PM


Question 53. Asked on :15 August 2020:05:14:34 PM

Write the full form of a.c.?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
Alternating current. 

-Answered by Shruti Srivastva On 15 August 2020:05:15:17 PM


Question 54. Asked on :15 August 2020:05:13:21 PM

Write the full form of d.c.?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva

direct current. 

-Answered by Shruti Srivastva On 15 August 2020:05:14:19 PM


Question 55. Asked on :15 August 2020:05:09:39 PM

What is the frequency of direct current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
zero.

-Answered by Shruti Srivastva On 15 August 2020:05:10:21 PM


Question 56. Asked on :15 August 2020:05:06:40 PM

What is an alternating current?

-Added by Shruti Srivastva Physics » Alternating Current And Electrical Machines

Answer:

Shruti Srivastva
It is that current which changes continously in magnitude and periodically in direction. 

-Answered by Shruti Srivastva On 15 August 2020:05:08:10 PM


 

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