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.
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 = Resistance at t°C.
R0 = Resistance at 0°C.
α = Temperature co-efficient.
t = 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.
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
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.
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 = Resistance at t°C.
R0 = Resistance at 0°C.
α = Temperature co-efficient.
t = 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.
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
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