Basic Electrical/Capacitance/Set-1/Paper-03

Q1. A consists of two

(a) insulation separated by dielectric (b) conductors separated by an insulator
(c) ceramic plates and one mica disc (d) conductors separated by air medium

Q2.  The capacitance of a capacitor is NOT influenced by

(a) plate thickness     (b)plate area   (c) plate separation    (d)nature of  dielectric

Q3.  A capacitor that stores a charge of 0.5 C at 10 volts has a capacitance of ________

(a) 5           (b)20             (c)10               (d)0.05

Q4. In a capacitor, the electric charges is stored in _________________

(a)metal plate (b)dielectric     (c)both a &b   (d)none of the above

Q5.  In a parallel plate capacitor, if a dielectric slab is introduced, then

(a)potential difference between plate will decrease
(b) electric intensity will decrease
(c) capacitance will increase
(d) all of the above



__________________________________SOLUTION________________________________

Q1. b
Q2. a

Q3.d

 C = 0.5/10 = 0.05 F

Q4.b
Q5.d

Basic Electrical/Resistance/Level-1/Paper-01

Q1. Two wires A and B have the same cross-section and are made of the same material. Ra  =600 ohm ad Rb =100 ohm. The number of times A is longer than B is

 (a) 6               (b)2                         (c) 4              (d)5

Ans: a

Q2. Two copper conductor have same length but one has cross-section twice that of the other. If thicker has a resistance of 20 ohm, the resistance of the other is ____________ohm

(a)10                (b)40                 (c)20                  (d)60

Ans:b

Hint :  A1= 2A2

Q3. Which of the following material has nearly zero temperature coefficient of resistance  ?

 (a)manganin           (b)porcelain        (c)copper                   (d)carbon

Ans:a

Q4. Which of the  following does not have negative temperature coefficient ?

 (a)Paper              ( b)Aluminium                        (c) Rubber                  (d) Mica

Ans: b

Q5. Resistance of a material always decreases if

  (a) temperature of material  is decreased
  (b) temperature of material  is increased
  (c) number of  free electrons available become more
  (d) none of the above is correct

Ans: c

Hysteresis loop or B-H curve

A B-H curve is used to show the relationship  between magnetic flux density (B)  and magnetic filed strength (H) for a material.The area of the hysteresis loop is related to the hysteresis loss.The area of hysteresis loop of a material is large, the hysteresis loss in this material will be large.Narrow hysteresis loops also have high permeability (the slope of B with respect to H) and magnetization.

                                                                 Hysteresis loop or B-H curve

Retentivity is a material's ability to retain a certain amount of residual magnetic field when the magnetizing force is removed after achieving saturation.

Coercive Force : The amount of reverse magnetic field which must be applied to a magnetic material to make the magnetic flux return to zero. 

Non retentive or soft  magnetic materials :

Soft (ferro) magnetic materials have a narrow hysteresis loop and they are easily magnetized. High saturation magnetization and a low coercivity (narrow B-H curve).Non retentive  magnetic materials  having  low magnetic losses and narrow hysteresis loop.

Retentive or hard magnetic materials :

Hard (ferro)  magnetic materials material such as cobalt steel retain their magnetism for long period of time, when  the magnetizing field is removed. i.e. They can act as a permanent magnet .Retentive or  hard  magnetic material  having high coercivity , high losses and large hysteresis loop 

Table 1 :  Narrow Vs Larger hysteresis loop area

Narrow hysteresis loop	Larger hysteresis loop
Soft (Ferro) magnetic    materials, have small coercive force	Hard (ferro) magnetic  materials have large coercive force
Lower - Retentivity,Coercivity, Reluctance, Residual Magnetism	Higher  - Retentivity,Coercivity , Reluctance, Residual Magnetism
Higher - Permeability	Lower - Permeability

                                            

Basic Electrical/Transformer/Page-01

This blog is an attempt to help you familiarize  electrical engineering competitive exam questions and answers.
The standard for the exam will be expect of an engineering holder.
This question paper may include the  following type of questions

• Direct questions contains - direct Theory and definition questions
• Problems - apply Mathematical formula for the solution.
• Advanced level questions include Design & application level questions
• Tricky or twisted question

1. Transformers are rated in

     (a)kV     (b)kW        (c) kWH       (d)KVA

Ans: d

2. The  transformer works on the principle of
     (a) static induction                  (b) self induction           (c) mutual induction    (d) both a and b
Ans: d

3. Transformer is used to change the vales of
          (a) Frequency (b) voltage (c) power (d)power factor
Ans:b

Tips: Transformer is used to change the values of  voltage and current. Transformer does not change the frequency and wave form.

4. A transformer provides a path for magnetic flux of
     (a) high conductivity (b) high reluctance (c) low reluctance (d) low conductivity
Ans:c

5.The emf induced in a coil depends on
    (a) the number of its turns
     (b) the change of flux linked with it
     (c)the time taken to change the flux
    (d)all of the above
Ans: d

Broadband equipments

DSL TECHNOLOGY

•  Digital Subscriber Line (DSL)  uses the same telephone line as traditional  modem
• Provides simultaneous access to Web and Telephone
• DSL remains  always -on all the time
• On power failure , telephone line is still available like a standard telephone line.

DSL Equipment

        DSL uses two pieces of equipment, one on the customer end and one at the telephone Exchange.  At the customer's location there is a DSL modem. The  DSL Access Multiplexer (DSLAM) is to receive customer connections at the Telephone Exchange.

This  UTStarcom DSLAM  consists of a chassis capable of holding up to 5 ADSL line cards and 2 CONTROL CARDs.Each ADSL line card has 48 ADSL ports.

DSLAM  UTSTAR COM  

Preventive maintenance of  DSLAMs

1.      Daily physical checking the Optical Fiber link between DSLAM and RPR .

2.   Perform following checks at least on  DSLAMs  everyday and take necessary action

      if any  card / equipment is found faulty 

a.      Check the status of control card of DSLAM .

b.      Check the status of all Fans in DSLAM.

c.      Check the status of all cards of the DSLAM. 

3. Check the status of all ports of each card in DSLAM and try to reset the hanged ports in DSLAM

4. Cleaning of DSLAM filter whenever required .

The faulty card may be got replaced with a spare card if available immediately 

Do's and Don'ts for broadband customers

Do's 

1. No phone or Fax should be connected before splitter 
2. Check your usages regularly (once in a month)
3. Please clean your computer virus regularly
4. Please swich off the modem when not in use

Don'ts

       Please do not disclosure your broadband User ID and Password to anybody

NETWORK COMPONENTS

BNG - Broadband Network Gateway
RPR - Resilient Packet Ring
DSLAM - Digital Subscriber Line Access Multiplexer
CPE -  Customer Premises Equipment (modem)

DSL Technology multiple choice questions

1. To enable DSL technology  internet service provider must have a ________________ located in their          networks to interact with customer modem
    (a) DSLAM
    (b) RPR
    (c) LAN switch
    (d) None of these

Ans : a

2. DSLAM s are generally aggregated through _______________interface

     (a) FE
     (b) GE
     (c) both FE and GE
     (d) None of these

Ans:c

3. Which of this is the basic feature of DSLAM?
     (a) DSLAM aggregates the digital subscriber line (DSL)
     (b) DSLAM deliver data transmission over existing copper telephone lines
     (c) DSLAM seperate Voice and Data of the subscriber
     (d)All of the above

Ans: d

4. Which of these have supplied equipment for DSLAM in BSNL ?
     (a) UTSTARCOM
     (b) SIEMENS
     (c) HUAWEI
     (d) All of the above
Ans: d

5. Maximum frequency range of a copper pair is in
    (a) kilo Hertz
    (b) Mega Hertz
    (c) Giga Hertz
    (d) Terra Hertz

Ans: b