Unit-6
Electrical Utilities
Q1) Mention all the basic requirements of metal halides inside the arc tubes?
Sol: The basic requirements of the metal additive are mentioned below:
- The iodide vapor pressure must be relatively high enough.
- The energy level configuration of the metal must be robust to encourage a high percentage of the visible radiation.
- At the bulb wall operating temperature of the iodide of the metal must be stable.
- The excitation level of the metal atoms must be lower than the average of the excitation level of mercury
Q2) Why there reflective coating at both ends of metal halide lamp?
Sol: The metal halide lamp has an arc tube whose ends are taken to be treated with a reflective white coating that is used to redirect the energy back into the tube. A uniform temperature can be maintained over entire arc tube length due to short length.
Q3) Explain specifications of digital multimeter?
- Sol: D.C Voltage : this includes various d.c vtg ranges available along with the resolution and accuracy
- A.c Voltage : this includes various a.c vtg ranges available along with the resolution and accuracy.
- A.C current : this includes various a.c current ranges available along with the resolution and accuracy.
- Resistance : this includes the available resistance range typical six range are available from 200Ω to 20 MΩ the accuracy is
0.1% of reading + two digits + 0.002Ω on the lowest range. - Input Impedance : The i/p Impedance is about 10 MΩ on all the range
- Normal mode noise rejection : this indicates the ability of the meter
It is greater than 60 dB at 50 HZ while the common mode noise rejection is greater than 90 dB at 50 HZ and greater than 120 dB at d.c
7. Overload protection: The overload protection of 1000 V d.c and 75 0ɤ.m.s. a.c is provided.
8. Diode test: The vtg drop across the diode can be measured for which 1 mA + 10% of constant current source is used.
9. Conductance: It can display Conductance in siemens
10. Relative Reference: when RF1 button is pressed the displayed reading is stored as a reference and then subtracted from the subsequent readings to indicate only amount of deviation from the reference.
11. Frequency: The frequency ranges is 200HZ to 200 kHZ auto selection.
Q4) How power is generated through thermal power plant?
Sol: In these plants coal is burnt to produce high temperature and pressure steam in boiler. The steam produces a rotational motion when it passes through turbine. This turbine rotates and produces electricity. In India coal is present in abundance so they are commonly used. The resources used are easily available and cheap so they require less cost in installation. The main drawback of these plants is that they pollute the environment. As the coal is burnt to produce energy the leftover ash and the chimneys adds to the cost in the plant.
We conclude the working of thermal plant by noticing that chemical energy from coal is converted to heat and steam which the turbine converts to mechanical energy to rotate and produce electricity.
Q5) Explain the significance of earthing with any two types?
Sol: It means connecting electrical equipment to earth with very low resistance wire. This ensures safe discharge of electrical energy due to failure of the insulation line coming in contact with the casing, etc. Earthing brings the potential of the body of the equipment to zero.
The main purpose of Earthing is to protect the operating personnel from shock. Under unbalanced load maintain the line voltage. To avoid risk of fire due to leakage currents. For protecting the equipment.
Methods of Earthing:
(i) Plate earthing: A copper plate of dimension 60cm x 60cm x 3.18 is used for earthing. The plate is buried in ground and layered with coal and salt. Then water is poured to maintain the earth’s electrode resistance below maximum value. The earth wire is bolted to the earth plate.
(ii) Pipe earthing:
The earth’s electrode made of galvanized iron pipe with holes on surface is placed upright in wet ground. In order to maintain the earth’s resistance, the pipe is filled with mixture of salt and coal. 
This system can carry larger leakage currents compared to plate earthing method.
Q6) List the safety precautions to be taken while working wth electrical equipment?
Sol:
The primary measures required to keep ourself and the equipment Safe are listed below
i) The hands or the equipment to be repaired or checked should not have any trace of water on it.
Ii) The equipment should not be of damaged insulation or broken chords.
Iii) The equipment before installation should be tested first.
Iv) The instruments should be identified and checked properly before fitting.
v) The site of work should have a board to notify that work is in progress.
Vi) The site where work is going on installation or any repair should be done after the site is earthed properly.
Vii) During heavy lighting and storm avoid working with electrical equipment.
Viii) The tools used while working should not be tossed it should be delivery by hand to the other person.
Ix) The shoes with rubber soles should be worn during work.
x) Insulated tools should be used.
Xi) If we have to repair anything at home always turn off the mains first.
Xii) Proper insulated rubber gloves and googles should be used.
Xiii) Always a wooden ladder should be used, avoid using steel ladders during work.
Xiv) Remember wire code of the country.
Xv) Never repair energised equipment, take and tester check first than use.
Q7) What are CFL explain with working?
Sol: CFL (Compact Fluorescent Lamp): They are the smaller version of common fluorescent lights which are used. The old CFLs had delay or flicker when turned on because they used magnetic ballasts. The new CFLs use magnetic ballasts. The CFLs life equivalent to 10 incandescent lamps.
Construction
The traditional fluorescent lamp tube is only used here. This tube is bent into compact size such that it gets fixed in ordinary incandescent fixtures.
It consists of a soda lime glass tube which is filled with argon and a drop of mercury. The tube end is sealed with metal electrodes, they conduct electricity from the external circuit to the gas inside tube. The main parts of CFL are gas filled tube and the electronic blast. An electrical current from the ballast flows through the mercury vapor,emitting ultraviolet light.This, ultraviolet light further excites a phosphor coating present inside the tube.The coating is responsible for emitting visible light. They require more energy when they are turned on. It takes 30 seconds to 3minutes for the electricity to pass through the bulb and get it started. It happens so because the lamp also requires a current to preheat the filaments, a high voltage for ignition and finally a high frequency AC current for running. The electronic blast first converts AC to DC at low frequency in input and again converting DC to AC at the output on high frequency.
Q8) How solar electric energy can be used? Explain briefly.
I) Sol: Here PV cells are used which are made of silicon.
a) Solar Photovoltaic: As soon as PV cells are exposed to light the electrons are released and current is produced. The cell is covered with metal grid to direct the flow of current. These cells connected in a panel are also used. These PV panels are installed above the roof. These panels are connected in series or parallel. The generation of power depends upon the amount of heat received from sun.
b) Solar water pumps: The motor required to run the pump uses electricity generated by solar panels. It consists of a photovoltaic array mounted on a stand and a motor-pump set compatible with the photovoltaic array. It converts the solar energy into electricity, which is used for running the motor pump set. The pumping system draws water from the open well, bore well, stream, pond, canal etc
Q9) How the power consumption in godown wiring is not affected by the number of loads connected?
Sol: These wirings are used to operate lamps in the godowns. The circuit is shown below with lamps. The arrangements are made such that when one light is turned on the other automatically gets switched off.
The common pole of first switch is connected to phase. The first throw of switch is connected to load and other to the common pole of next switch. In unused state the common poles of all switches are at first throw of switch.In such an arrangement, changing the switch position to 2nd throw OFF’s previous load and ON the next one. There can be any number of loads depending on the requirements. The power consumption is not affected as only one lamp is on at any instance. The length of wire only increases with the number of loads.
Q10) What are SPDT switches and how they are used in staircase wiring?
Sol: The staircase wiring done with 2-way switch is explained below. These switches are called SPDT i.e single pole double throw switches. This helps us to use same wiring from different places.
The above shown is the circuit for 2-way switch. One switch is installed near first step and second switch at the upper end of stair. The supply is given to the switch at the short-circuited terminals. The connection to the light point is taken from the similar short-circuited terminal of the second switch, other two independent terminals of each circuit are connected through cables.
Unit-6
Electrical Utilities
Q1) Mention all the basic requirements of metal halides inside the arc tubes?
Sol: The basic requirements of the metal additive are mentioned below:
- The iodide vapor pressure must be relatively high enough.
- The energy level configuration of the metal must be robust to encourage a high percentage of the visible radiation.
- At the bulb wall operating temperature of the iodide of the metal must be stable.
- The excitation level of the metal atoms must be lower than the average of the excitation level of mercury
Q2) Why there reflective coating at both ends of metal halide lamp?
Sol: The metal halide lamp has an arc tube whose ends are taken to be treated with a reflective white coating that is used to redirect the energy back into the tube. A uniform temperature can be maintained over entire arc tube length due to short length.
Q3) Explain specifications of digital multimeter?
- Sol: D.C Voltage : this includes various d.c vtg ranges available along with the resolution and accuracy
- A.c Voltage : this includes various a.c vtg ranges available along with the resolution and accuracy.
- A.C current : this includes various a.c current ranges available along with the resolution and accuracy.
- Resistance : this includes the available resistance range typical six range are available from 200Ω to 20 MΩ the accuracy is
0.1% of reading + two digits + 0.002Ω on the lowest range. - Input Impedance : The i/p Impedance is about 10 MΩ on all the range
- Normal mode noise rejection : this indicates the ability of the meter
It is greater than 60 dB at 50 HZ while the common mode noise rejection is greater than 90 dB at 50 HZ and greater than 120 dB at d.c
7. Overload protection: The overload protection of 1000 V d.c and 75 0ɤ.m.s. a.c is provided.
8. Diode test: The vtg drop across the diode can be measured for which 1 mA + 10% of constant current source is used.
9. Conductance: It can display Conductance in siemens
10. Relative Reference: when RF1 button is pressed the displayed reading is stored as a reference and then subtracted from the subsequent readings to indicate only amount of deviation from the reference.
11. Frequency: The frequency ranges is 200HZ to 200 kHZ auto selection.
Q4) How power is generated through thermal power plant?
Sol: In these plants coal is burnt to produce high temperature and pressure steam in boiler. The steam produces a rotational motion when it passes through turbine. This turbine rotates and produces electricity. In India coal is present in abundance so they are commonly used. The resources used are easily available and cheap so they require less cost in installation. The main drawback of these plants is that they pollute the environment. As the coal is burnt to produce energy the leftover ash and the chimneys adds to the cost in the plant.
We conclude the working of thermal plant by noticing that chemical energy from coal is converted to heat and steam which the turbine converts to mechanical energy to rotate and produce electricity.
Q5) Explain the significance of earthing with any two types?
Sol: It means connecting electrical equipment to earth with very low resistance wire. This ensures safe discharge of electrical energy due to failure of the insulation line coming in contact with the casing, etc. Earthing brings the potential of the body of the equipment to zero.
The main purpose of Earthing is to protect the operating personnel from shock. Under unbalanced load maintain the line voltage. To avoid risk of fire due to leakage currents. For protecting the equipment.
Methods of Earthing:
(i) Plate earthing: A copper plate of dimension 60cm x 60cm x 3.18 is used for earthing. The plate is buried in ground and layered with coal and salt. Then water is poured to maintain the earth’s electrode resistance below maximum value. The earth wire is bolted to the earth plate.
(ii) Pipe earthing:
The earth’s electrode made of galvanized iron pipe with holes on surface is placed upright in wet ground. In order to maintain the earth’s resistance, the pipe is filled with mixture of salt and coal. 
This system can carry larger leakage currents compared to plate earthing method.
Q6) List the safety precautions to be taken while working wth electrical equipment?
Sol:
The primary measures required to keep ourself and the equipment Safe are listed below
i) The hands or the equipment to be repaired or checked should not have any trace of water on it.
Ii) The equipment should not be of damaged insulation or broken chords.
Iii) The equipment before installation should be tested first.
Iv) The instruments should be identified and checked properly before fitting.
v) The site of work should have a board to notify that work is in progress.
Vi) The site where work is going on installation or any repair should be done after the site is earthed properly.
Vii) During heavy lighting and storm avoid working with electrical equipment.
Viii) The tools used while working should not be tossed it should be delivery by hand to the other person.
Ix) The shoes with rubber soles should be worn during work.
x) Insulated tools should be used.
Xi) If we have to repair anything at home always turn off the mains first.
Xii) Proper insulated rubber gloves and googles should be used.
Xiii) Always a wooden ladder should be used, avoid using steel ladders during work.
Xiv) Remember wire code of the country.
Xv) Never repair energised equipment, take and tester check first than use.
Q7) What are CFL explain with working?
Sol: CFL (Compact Fluorescent Lamp): They are the smaller version of common fluorescent lights which are used. The old CFLs had delay or flicker when turned on because they used magnetic ballasts. The new CFLs use magnetic ballasts. The CFLs life equivalent to 10 incandescent lamps.
Construction
The traditional fluorescent lamp tube is only used here. This tube is bent into compact size such that it gets fixed in ordinary incandescent fixtures.
It consists of a soda lime glass tube which is filled with argon and a drop of mercury. The tube end is sealed with metal electrodes, they conduct electricity from the external circuit to the gas inside tube. The main parts of CFL are gas filled tube and the electronic blast. An electrical current from the ballast flows through the mercury vapor,emitting ultraviolet light.This, ultraviolet light further excites a phosphor coating present inside the tube.The coating is responsible for emitting visible light. They require more energy when they are turned on. It takes 30 seconds to 3minutes for the electricity to pass through the bulb and get it started. It happens so because the lamp also requires a current to preheat the filaments, a high voltage for ignition and finally a high frequency AC current for running. The electronic blast first converts AC to DC at low frequency in input and again converting DC to AC at the output on high frequency.
Q8) How solar electric energy can be used? Explain briefly.
I) Sol: Here PV cells are used which are made of silicon.
a) Solar Photovoltaic: As soon as PV cells are exposed to light the electrons are released and current is produced. The cell is covered with metal grid to direct the flow of current. These cells connected in a panel are also used. These PV panels are installed above the roof. These panels are connected in series or parallel. The generation of power depends upon the amount of heat received from sun.
b) Solar water pumps: The motor required to run the pump uses electricity generated by solar panels. It consists of a photovoltaic array mounted on a stand and a motor-pump set compatible with the photovoltaic array. It converts the solar energy into electricity, which is used for running the motor pump set. The pumping system draws water from the open well, bore well, stream, pond, canal etc
Q9) How the power consumption in godown wiring is not affected by the number of loads connected?
Sol: These wirings are used to operate lamps in the godowns. The circuit is shown below with lamps. The arrangements are made such that when one light is turned on the other automatically gets switched off.
The common pole of first switch is connected to phase. The first throw of switch is connected to load and other to the common pole of next switch. In unused state the common poles of all switches are at first throw of switch.In such an arrangement, changing the switch position to 2nd throw OFF’s previous load and ON the next one. There can be any number of loads depending on the requirements. The power consumption is not affected as only one lamp is on at any instance. The length of wire only increases with the number of loads.
Q10) What are SPDT switches and how they are used in staircase wiring?
Sol: The staircase wiring done with 2-way switch is explained below. These switches are called SPDT i.e single pole double throw switches. This helps us to use same wiring from different places.
The above shown is the circuit for 2-way switch. One switch is installed near first step and second switch at the upper end of stair. The supply is given to the switch at the short-circuited terminals. The connection to the light point is taken from the similar short-circuited terminal of the second switch, other two independent terminals of each circuit are connected through cables.
Unit-6
Electrical Utilities
Q1) Mention all the basic requirements of metal halides inside the arc tubes?
Sol: The basic requirements of the metal additive are mentioned below:
- The iodide vapor pressure must be relatively high enough.
- The energy level configuration of the metal must be robust to encourage a high percentage of the visible radiation.
- At the bulb wall operating temperature of the iodide of the metal must be stable.
- The excitation level of the metal atoms must be lower than the average of the excitation level of mercury
Q2) Why there reflective coating at both ends of metal halide lamp?
Sol: The metal halide lamp has an arc tube whose ends are taken to be treated with a reflective white coating that is used to redirect the energy back into the tube. A uniform temperature can be maintained over entire arc tube length due to short length.
Q3) Explain specifications of digital multimeter?
- Sol: D.C Voltage : this includes various d.c vtg ranges available along with the resolution and accuracy
- A.c Voltage : this includes various a.c vtg ranges available along with the resolution and accuracy.
- A.C current : this includes various a.c current ranges available along with the resolution and accuracy.
- Resistance : this includes the available resistance range typical six range are available from 200Ω to 20 MΩ the accuracy is
0.1% of reading + two digits + 0.002Ω on the lowest range. - Input Impedance : The i/p Impedance is about 10 MΩ on all the range
- Normal mode noise rejection : this indicates the ability of the meter
It is greater than 60 dB at 50 HZ while the common mode noise rejection is greater than 90 dB at 50 HZ and greater than 120 dB at d.c
7. Overload protection: The overload protection of 1000 V d.c and 75 0ɤ.m.s. a.c is provided.
8. Diode test: The vtg drop across the diode can be measured for which 1 mA + 10% of constant current source is used.
9. Conductance: It can display Conductance in siemens
10. Relative Reference: when RF1 button is pressed the displayed reading is stored as a reference and then subtracted from the subsequent readings to indicate only amount of deviation from the reference.
11. Frequency: The frequency ranges is 200HZ to 200 kHZ auto selection.
Q4) How power is generated through thermal power plant?
Sol: In these plants coal is burnt to produce high temperature and pressure steam in boiler. The steam produces a rotational motion when it passes through turbine. This turbine rotates and produces electricity. In India coal is present in abundance so they are commonly used. The resources used are easily available and cheap so they require less cost in installation. The main drawback of these plants is that they pollute the environment. As the coal is burnt to produce energy the leftover ash and the chimneys adds to the cost in the plant.
We conclude the working of thermal plant by noticing that chemical energy from coal is converted to heat and steam which the turbine converts to mechanical energy to rotate and produce electricity.
Q5) Explain the significance of earthing with any two types?
Sol: It means connecting electrical equipment to earth with very low resistance wire. This ensures safe discharge of electrical energy due to failure of the insulation line coming in contact with the casing, etc. Earthing brings the potential of the body of the equipment to zero.
The main purpose of Earthing is to protect the operating personnel from shock. Under unbalanced load maintain the line voltage. To avoid risk of fire due to leakage currents. For protecting the equipment.
Methods of Earthing:
(i) Plate earthing: A copper plate of dimension 60cm x 60cm x 3.18 is used for earthing. The plate is buried in ground and layered with coal and salt. Then water is poured to maintain the earth’s electrode resistance below maximum value. The earth wire is bolted to the earth plate.
(ii) Pipe earthing:
The earth’s electrode made of galvanized iron pipe with holes on surface is placed upright in wet ground. In order to maintain the earth’s resistance, the pipe is filled with mixture of salt and coal. 
This system can carry larger leakage currents compared to plate earthing method.
Q6) List the safety precautions to be taken while working wth electrical equipment?
Sol:
The primary measures required to keep ourself and the equipment Safe are listed below
i) The hands or the equipment to be repaired or checked should not have any trace of water on it.
Ii) The equipment should not be of damaged insulation or broken chords.
Iii) The equipment before installation should be tested first.
Iv) The instruments should be identified and checked properly before fitting.
v) The site of work should have a board to notify that work is in progress.
Vi) The site where work is going on installation or any repair should be done after the site is earthed properly.
Vii) During heavy lighting and storm avoid working with electrical equipment.
Viii) The tools used while working should not be tossed it should be delivery by hand to the other person.
Ix) The shoes with rubber soles should be worn during work.
x) Insulated tools should be used.
Xi) If we have to repair anything at home always turn off the mains first.
Xii) Proper insulated rubber gloves and googles should be used.
Xiii) Always a wooden ladder should be used, avoid using steel ladders during work.
Xiv) Remember wire code of the country.
Xv) Never repair energised equipment, take and tester check first than use.
Q7) What are CFL explain with working?
Sol: CFL (Compact Fluorescent Lamp): They are the smaller version of common fluorescent lights which are used. The old CFLs had delay or flicker when turned on because they used magnetic ballasts. The new CFLs use magnetic ballasts. The CFLs life equivalent to 10 incandescent lamps.
Construction
The traditional fluorescent lamp tube is only used here. This tube is bent into compact size such that it gets fixed in ordinary incandescent fixtures.
It consists of a soda lime glass tube which is filled with argon and a drop of mercury. The tube end is sealed with metal electrodes, they conduct electricity from the external circuit to the gas inside tube. The main parts of CFL are gas filled tube and the electronic blast. An electrical current from the ballast flows through the mercury vapor,emitting ultraviolet light.This, ultraviolet light further excites a phosphor coating present inside the tube.The coating is responsible for emitting visible light. They require more energy when they are turned on. It takes 30 seconds to 3minutes for the electricity to pass through the bulb and get it started. It happens so because the lamp also requires a current to preheat the filaments, a high voltage for ignition and finally a high frequency AC current for running. The electronic blast first converts AC to DC at low frequency in input and again converting DC to AC at the output on high frequency.
Q8) How solar electric energy can be used? Explain briefly.
I) Sol: Here PV cells are used which are made of silicon.
a) Solar Photovoltaic: As soon as PV cells are exposed to light the electrons are released and current is produced. The cell is covered with metal grid to direct the flow of current. These cells connected in a panel are also used. These PV panels are installed above the roof. These panels are connected in series or parallel. The generation of power depends upon the amount of heat received from sun.
b) Solar water pumps: The motor required to run the pump uses electricity generated by solar panels. It consists of a photovoltaic array mounted on a stand and a motor-pump set compatible with the photovoltaic array. It converts the solar energy into electricity, which is used for running the motor pump set. The pumping system draws water from the open well, bore well, stream, pond, canal etc
Q9) How the power consumption in godown wiring is not affected by the number of loads connected?
Sol: These wirings are used to operate lamps in the godowns. The circuit is shown below with lamps. The arrangements are made such that when one light is turned on the other automatically gets switched off.
The common pole of first switch is connected to phase. The first throw of switch is connected to load and other to the common pole of next switch. In unused state the common poles of all switches are at first throw of switch.In such an arrangement, changing the switch position to 2nd throw OFF’s previous load and ON the next one. There can be any number of loads depending on the requirements. The power consumption is not affected as only one lamp is on at any instance. The length of wire only increases with the number of loads.
Q10) What are SPDT switches and how they are used in staircase wiring?
Sol: The staircase wiring done with 2-way switch is explained below. These switches are called SPDT i.e single pole double throw switches. This helps us to use same wiring from different places.
The above shown is the circuit for 2-way switch. One switch is installed near first step and second switch at the upper end of stair. The supply is given to the switch at the short-circuited terminals. The connection to the light point is taken from the similar short-circuited terminal of the second switch, other two independent terminals of each circuit are connected through cables.
