1. What is static electricity?
Static electricity means electricity at rest. If we join a charged conductor to another conductor, electricity flows from one to the other. This way an electric current is produced, which lasts for a moment only. Static electricity is no use. Rubbing of two different materials having different electrons produces this.
2. What is current?
Flow of electrons in any conductor is called electric current. Its symbol is ‘I’ and measuring unit is Ampere measured by ammeter or ampere meter.
3. What is electro-motive force (emf) or voltage?
It is the pressure that moves the electrons to flow in any conductor. It is also known as electromotive force voltage. Its symbol is ‘E’ or ‘V’ and measuring unit is volt measured by voltmeter.
4. What is potential difference (P.D)?
The difference of potential between two points in a circuit is the voltage required to drive the current between them or the voltage drop between those two points is called the potential difference. P.D = R * I volts. 5. What is terminal voltage (VT)? It is the voltage available at the terminal of the source of supply. It’s symbol is VT. VT = emf – P.D
6. What is resistance?
Resistance is the property of a substance, which gives opposition to flow of electrons through itself. Its measuring unit is ohm and measured by ohmmeter, multi meter, wheat stone bridge, and post office box. There are two types of resistances and they are fixed resistance and variable resistance.
7. What is ampere?
The international ampere is defined as that steady current which, flowing through a solution of silver nitrate, deposits silver at the rate of 0.001118 gm/sec.
8. What is volt?
The international volt is defined as 1/1.0183 of the emf of a Weston cadmium cell. It is that difference of potential which, when applied to a conductor whose resistance is 1 (one) international ohm, will cause a current of 1 (one) international ampere to flow. Question and answers Electrical Maintenance
9. What is matter?
The matter is defined as anything, which possesses weight and occupies space and can be in any of three forms solid, liquid or gaseous. The matter consists of three ingredients, which are protons, neutrons and electrons.
10. What is the speed of electricity or electrons?
The speed of electricity or electrons is 297842 km (186000 miles) per second.
11. How we get electric shock?
On all alternators, transformers neutral is earthed. Human body is conductor and when touched to the live conductor it completes its shortest root though the body and the body gets electric shock in which its nervous system, the heart, respiratory system may cease to function.
12. What is fuse and what materials used for fuse wire?
Fuse is a weakest point in an electrical circuit, which melts when the excess current flows through it in the electrical circuit. The materials, which can be used in fuses, are tin, lead, zinc, silver, antimony, copper, and aluminium, etc.
13. What is fusing factor?
The ratio of minimum fusing current and the current rating of fusing element is called the fusing factor. Fusing factor = minimum fusing current / current rating of fusing element. Its value is always more than 1 (one).
14. What is soldering and what is brazing?
Soldering is the process of joining two metals with an alloy whose melting point is less that of the materials to be soldered. Soldering at high temperature using brass as solder is called brazing or hard soldering. The composition of the fine solder (soft solder) is tin 60% and lead 40%. Its melting point is 190°C and is widely used.
15. What are the sources of electricity?
a. Battery (chemical source)
b. Generator (magnetism)
c. Thermocouple (heat generated)
d. Light (photo electric or solar cell)
e. Pressure (piezo electricity)
f. Friction (static electricity)
16. What are the effects of electric current?
a. Physical effect.
b. Chemical effect.
c. Magnetic effect.
d. Heating effect.
e. X-ray effect.
17. What is fire?
Destructive burning of any material is called the fire. Fire is the result of combining fuel, oxygen and heat. If any one among three is separated the fire will come to end.
18. On what factor resistance of the substance depends (Laws of resistance)?
a. The resistance of the conductor is directly proportional to the length of the conductor.
b. The resistance of the conductor is inversely proportional to the cross-section of the conductor.
c. The resistance of the conductor depends on the nature of the material by which it is made.
That is specific resistance of the material.
d. The resistance of the conductor depends on its temperature. The formula to find the resistance of the substance is below. R = ρ L Ω A Where ρ is the constant for the material called its specific resistance or resistivity.
19. What is specific resistance or resistivity of the material?
Specific resistance of the material is the resistance of a piece of unit length and unit cross-section (unit cube of that material). That is the resistance between the opposite faces of unit cube of the material. Or the specific resistance of any material is the resistance offered by the opposite face of that material. The unit of specific resistance is Ω/cm3 , Ω/inch3 , Ω/m3 .
20. What is the temperature co-efficient of resistance?
Temperature co-efficient of the resistance of any substance is, change in its original resistance due to the change in temperature. The temperature co-efficient of resistance of material is the ratio of increase in resistance of 1°C rise in temperature to the original resistance of the material (strictly at 0°C). Formula for the resistance measurement is, Rt = R0 (1+αt) Where Rt Æ Resistance at t°C. R0 Æ Resistance at 0°C. α Æ Temperature co-efficient. t Æ Temperature rise.
21. What are the effects of temperature on resistance?
The effects of temperature on resistance are
a. In certain pure metals such as gold, copper, silver, aluminium etc. the resistance increases with increasing temperature at fairly regular manner. Such metals possess positive temperature co-efficient of resistance.
b. In certain materials (alloys) such as eureka, nichrome etc. the change in resistance due to increasing temperature is irregular and negligible for a considerable range of temperature.
c. In case of certain materials belongs to insulators, electrolytes such as paper, rubber, glass, mica, carbon, acids, alkalies etc. the resistance decreases with increasing temperature at fairly regular manner. Such materials posses negative co-efficient of resistance.
22. What are the classifications of voltages?
a. Low voltage: Voltage not exceeding 250V. That is 0 – 250V.
b. Medium voltage: Voltage above 250V upto 650V comes under medium voltage.
c. High voltage: Voltage above 650V upto 33 kV comes under high voltage.
d. Extra high voltage: Above 33 kV voltages are extra high voltages.
23. What is coulomb?
It is the unit of charge. One (1) coulomb is the quantity of electricity, which is circulated by a current of one (1) ampere in one second. The letter Q denotes it. So that 1 coulomb = 1 amp * 1 second.
24. What is farad?
Farad is the unit of capacitance and the letter F denotes it. A condenser has a capacitance of one (1) farad, if it is capable to maintain a charge of one coulomb under a potential difference of one volt between its plates. Question and answers Electrical Maintenance Unit - 5 - 1 farad = 1 coulomb / 1 volt. = Q/V.
25. What is henry?
It is the unit of inductance and the letter H denotes it. A circuit has inductance of one henry, if an electro-motive force of one volt if induced in that circuit, when the current in that circuit changes at the rate of one ampere per second. 1 henry = 1 volt sec / ampere.
26. What is the least count of out-side micrometer?
The least count of out-side micrometer is 0.01mm.
29. What is conductance?
Conductance is the property of the conductor, which allows the flow of electric current through it. Conductance is denoted by the letter G and is reciprocal of resistance. The unit of conductance is mho. A substance, which posses conductance as its major property can be called as a good conductor.
30. What you mean by insulator?
What are the qualities of good insulator?
A substance, which will not allow the flow of electric current to pass through it is called the insulator. The conductance and conductivity is zero in insulators. Insulators are used to isolate the electric current from neighbouring parts. Insulators will not allow the leakage of current, short-circuiting current, shock to the operator and isolates the electric current safely with out any diversion to any other place. Qualities of good insulator a. It should be flexible b. It should have good mechanical strength c. It should easily moulded into any shape d. It should not be effected by acid e. It should be non-inflammable f. It should have very high specific resistance to prevent leakage current g. It should be withstand high temperature. Because insulators posses negative temperature coefficient of resistance. That is resistance decreases with increasing temperature h. It should have high dielectric strength
31. What is electrode?
A conducting element used for converging (centering) current to and from a medium is called electrode. There are two types of electrode. A positive and other is negative.
32. What is force?
Force is that which charge or tends to change a body state of rest or uniform motion through a straight line. The unit of force is Newton.
33. What is Newton?
One Newton is that amount of force which acting on one-kilogram mass for one second gives an acceleration 1 meter/sec/sec.
34. What is weight?
Weight is the gravitation force by which a body attracted to the earth. Gravitational unit of force in M.K.S system is kilogram weight or 9.81 Newton. Weight is the force with which 1-kilogram mass is attracted by the earth towards its center.
35. What is bayer?
Bayer is the C.G.S unit of pressure and is equal to 1-dyne/cm2 .
36. What is conductor?
Substances such as metals, which have large number of free electrons are said to offer a low resistance to the flow of electrons under the influence of emf and hence are called conductors. Conductors are used to conduct electricity from one place to another place due to its major property conductance. Conductors are classified into three main groups. a. Good conductors. b. Semi conductors. c. Fair conductors.
37. What are the properties of good conductor?
Properties of good conductor
a. It posses very low resistance or specific resistance.
b. It posses more conductance and there by conducts electricity readily through it.
c. It is a good conductor of heat.
d. It is highly resistance to corrosion by liquid.
e. It must be malleable and ductile.
f. It must be flexible.
g. It posses better tensile strength.
h. It should not react with climatic conditions.
i. It can be drawn in very fine wires.
j. It must be readily joinable.
k. It must be very low in cost.
l. It must available in plenty.
37. What are the common conductors in sequence with high conductivity?
a. Silver
b. Silver copper alloy
c. Copper (Hard down and Annealed)
d. Gold
e. Zinc
f. Platinum
g. Tin
h. Aluminum
i. Iron
j. Brass
k. Phosphorous bronze
l. Nickel
m. Lead
n. Germanium silver
o. Antimony
p. Platinoid
q. Mercury
r. Bismuth
s. Platinum iridium
38. What is semiconductor?
Semiconductors posses less conductivity (conductance) than good conductors. That is semiconductors gives opposition (resistance) to the flow of free electrons than that of good conductor. Examples for semiconductor are
a. Dilute acid
b. Metallic ores
c. See water
d. Moist earth
e. Silicone
f. Germanium
39. What is fair conductor?
Fair conductors are the materials, which have less conductivity than that of semiconductor. Fair conductor gives more opposition to the flow of free electrons than that of semiconductors. Examples for fair conductors are
a. Charcoal
b. Coke
c. Carbon
d. Plumbago
40. What is resistor?
Resistors posses high resistance, but less conductance. This property is well utilized to convert electrical energy into heat energy. Common application of resistors is production of heaters. Examples are eureka, carbon, nichrome, tungsten, manganin, germanium, and tentalum. In case of heaters, electrical iron and soldering iron etc the heating element are made of nichrome, but in lamps filament is made of tungsten.
41. What is the difference between resistor, rheostat and potential divider?
Resistor:
a fixed resistance connected permanently in the circuit for limiting the current to definite value is called the resistor.
Rheostat:
a variable resistance by sliding contacts on it the current can be varied is called rheostat.
Potential divider:
when a resistance is used to develop a voltage drop it is called a potential divider.
42. What is solder?
Solder is an alloy of lead and tin mixed in different proposition as per the work to be done. In some cases certain % of bismuth and cadmium is also added to decrease the melting point of the solder. Antimony increases the melting point of the solder. Bismuth has a special quality in comparing to most of other metals. That is it expands when it cools. This property helps to shrink the solder and there by it allows the joint become firm. The quality of the solder depends on the % of tin in the solder. To get stronger joint add more tin in the solder. For electrical work fine solder of 1½ part tin and 1 part lead is used and for sheet metal works soft solder of 1 part tin and 1 part lead is used.
43. What is flux?
Flux is a cleanser and is used to remove and prevent oxidation of the metals, allowing the solder to flow from and to, to unite the solder more firmly with the surface to be joined.
44. What is skin effect?
Electricity has affinity (fondness) to pass through peripheral surface of the conductor. This effect of electricity flowing through the peripheral surface of the conductor is known as skin effect.
45. What are the advantages of stranded cables?
a. It gives flexibility.
b. It prevents skin effect.
c. Increases current carrying capacity.
d. It provides easy in soldering joint.
e. If one strand breaks the other will carry the load current.
46. State the Ohm’s law.
In a closed electrical circuit, at a constant temperature, the ratio between the resulting unvarying current or direct current and applied voltage is a constant. That constant is known as resistance.
OR In simple manner Ohm’s law says that, in a closed electrical circuit the current is directly proportional to the voltage and inversely proportional to the resistance of the circuit. I = V/R or R = V/I or E = IR. Ohm's Law / Power Formulas P = watts I = amps R = ohms E = Volts
47. What is series circuit?
What are the characteristics of series circuit? It is that circuit where two or more electrical consuming devices are connected so as to provide only one path to the flow of current. Characteristics of series circuit a. It has only one path for the flow of current. b. If any breakage happens the whole system will be out of that circuit. c. It is very difficult to find the fault. d. Individual voltage drop depends on individual resistance (V = I rn). e. The total resistance of a series circuit is the sum of the individual resistance. f. Addition of the resistance increases total resistance and decreases the current. g. Individual device will not get its full efficiency.
48. What is parallel circuit?
What are the characteristics of parallel circuit?
It is that circuit where two or more electrical consuming devices are connected so as to provide as many parallel paths to the flow of current. Characteristics of parallel circuit
a. As many parallel paths as there are devices.
b. Individual devices will get its full efficiency.
c. Breakage in one circuit will not affect the other circuit.
d. Current in each device is different according to the resistance of the device.
e. If the individual resistance increases the total resistance will decrease (1/R = 1/ r1 + 1/ r2 +1/ rn)
f. The reciprocal of total resistance is equal to the sum of the reciprocal of individual parallel resistances (1/R = 1/ r1 + 1/ r2 +1/ rn).
g. Individual conductance is inversely proportional to the individual resistance.
h. If two same value resistors are connected in parallel circuit the total resistance is the resistance of one resistor. And the total of parallel circuit resistance will be less than the least resistance in that circuit.
49. What is capacitor?
On what factor capacity of a capacitor depends?
Capacitor or condenser is a device to store electrical energy and to release it into the circuit of which the capacitor forms a part. Capacity of a capacitor depends on following factors
a. Capacity of the capacitor is directly proportional to the area of the plate.
b. Capacity is inversely proportional to the distance between the plate. That is if the distance is more the capacity decreases or if the distance is less the capacity more.
c. It depends on the nature of dielectric constant.
50. On what factor voltage rating of the capacitor depend?
The voltage rating of the capacitor depends on the distance between the plates of the capacitor. If the voltage exceeds, the electrons across the space between the plates can result in permanent damage to the capacitor.
https://www.youtube.com/channel/UC4_D50vMu1wbQrPaLFYo6Eg https://www.youtube.com/channel/UC4_D50vMu1wbQrPaLFYo6Eg RRB JE, SSC AE/JE UPSSSC JE, SSC JE, CIVIL ENGINEERING MCQs, ELECTICAL ENGINEERING MCQs, preavious year quesion papers, dmrc, lmrc, drdo,rrb ntpc, ntpc, pgcil, dsssb, states board, GATE IES EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot Daily news & current affairs in hindi & english fully updated Daily current affairs https://t.me/newsdailypkr Engineering Discussion group for your upcoming exams, you can ask your any query regarding your problem,👇👇👇 https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA PKR ELECTRICAL ENGINEERING I am sure this is the best place for you guys subscribe and get success IF YOU WANT TO JOIN ME ON TELEGRAM FOR PDF @newsdailypkr AE/JE EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot facebook page:- Pravendra Kumar Rajpoot https://t.me/newsdailypkr https://chat.whatsapp.com/5AS7dNFTP4H4vVsiWsqHrT https://t.me/srk50 https://t.me/pravendrarajpoot https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA https://t.me/pravendrarajpoot Daily news & current affairs in hindi & english fully updated Daily current affairs https://t.me/newsdailypkr Engineering Discussion group for your upcoming exams, you can ask your any query regarding your problem,👇👇👇 https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA PKR ELECTRICAL ENGINEERING I am sure this is the best place for you guys subscribe and get success IF YOU WANT TO JOIN ME ON TELEGRAM FOR PDF @newsdailypkr AE/JE EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot facebook page:- Pravendra Kumar Rajpoot https://t.me/newsdailypkr https://chat.whatsapp.com/5AS7dNFTP4H4vVsiWsqHrT https://t.me/srk50 https://t.me/pravendrarajpoot https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA
No comments:
Post a Comment