Illumination MCQ Quiz - Objective Question with Answer for Illumination - Download Free PDF

Explanation:

Critical Consideration in Street Lighting Design and Estimation

Definition: Designing and estimating the cost of street lighting systems involves various technical, economic, and environmental considerations. One of the most critical aspects is calculating the number of light fixtures, cable requirements, and energy consumption to determine overall costs. This ensures that the lighting system meets performance standards while remaining cost-effective and sustainable.

Working Principle:

The process of designing a street lighting system begins with assessing the area to be illuminated. This involves determining the spacing and placement of light fixtures to ensure uniform light distribution. Engineers calculate the required lumen output, taking into account factors such as road width, pedestrian pathways, and traffic density. Once the layout is finalized, cable requirements are estimated based on the power supply network and the distance between fixtures. Energy consumption is then calculated to estimate operational costs and explore energy-efficient solutions.

Advantages of Proper Cost Estimation:

• Ensures adequate illumination levels to improve safety for pedestrians and drivers.
• Optimizes the use of resources, reducing waste and unnecessary expenses.
• Supports the integration of energy-efficient technologies, lowering long-term operational costs.
• Facilitates compliance with regulatory standards and environmental guidelines.

Steps Involved:

1. Determine the area to be illuminated, including roadways, sidewalks, intersections, and public spaces.
2. Calculate the number of light fixtures required based on illumination standards and area dimensions.
3. Estimate cable requirements by analyzing the power distribution network and fixture placement.
4. Evaluate energy consumption using the wattage of light fixtures and operational hours.
5. Incorporate energy-efficient lighting solutions, such as LED technology, to reduce electricity usage.
6. Factor in installation, maintenance, and operational costs to determine the total budget.

Applications:

This methodology is applied in designing street lighting systems for urban areas, highways, parking lots, and public parks. Proper estimation and design enhance public safety, reduce energy consumption, and contribute to sustainable urban development.

Correct Option Analysis:

The correct option is:

Option 1: Calculating the number of light fixtures, cable requirements, and energy consumption to determine overall costs.

This option emphasizes the importance of a comprehensive approach to street lighting design and cost estimation. By considering the number of fixtures, cable requirements, and energy consumption, engineers can create an efficient and cost-effective lighting system that meets performance standards and sustainability goals.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 2: Focusing only on the aesthetic design of the streetlights.

This option is incorrect as aesthetics alone cannot ensure the functionality, safety, and cost-effectiveness of a street lighting system. While aesthetic design is important for urban appeal, it must be balanced with technical and economic considerations to create an efficient lighting system.

Option 3: Ignoring energy efficiency to reduce initial costs.

This approach is counterproductive in the long run. Ignoring energy efficiency might lower initial installation costs but leads to higher operational expenses due to increased energy consumption. Energy-efficient solutions, such as LED lighting, provide significant savings over time and contribute to environmental sustainability.

Option 4: Eliminating the use of protective devices in the system.

Protective devices, such as circuit breakers and surge protectors, are essential for ensuring the safety and reliability of the street lighting system. Eliminating them compromises the system’s durability and increases the risk of damage due to electrical faults or power surges.

Conclusion:

Effective street lighting design and estimation require a comprehensive approach that balances technical, economic, and environmental considerations. Calculating the number of light fixtures, cable requirements, and energy consumption is fundamental to achieving a functional and cost-effective lighting system. Ignoring aspects like energy efficiency, protective devices, or focusing solely on aesthetics leads to suboptimal solutions that fail to meet the demands of modern urban infrastructure.

Explanation:

Critical Factor in Cable Selection for Outdoor Public Lighting Installations

Definition: When designing and installing outdoor public lighting systems, the selection of cables is a crucial aspect that ensures the system operates efficiently, safely, and reliably under various environmental conditions. Cables act as the medium for transmitting electrical power to the lighting fixtures, and their selection must align with the requirements of the installation environment and the electrical load.

Correct Option Analysis:

The correct option is:

Option 2: The cable's ability to withstand environmental conditions and carry the required current safely.

This option emphasizes the importance of selecting cables that can endure the specific environmental conditions of outdoor public lighting installations while also meeting the electrical load requirements. This involves considering several critical factors:

• Environmental Conditions: Outdoor cables are exposed to varying weather conditions, such as rain, extreme heat, cold, UV radiation, and potential mechanical stresses. Hence, the cables must have adequate insulation and outer sheathing to resist these factors effectively.
• Current Carrying Capacity: The cable must be capable of safely carrying the required current without overheating. This involves choosing the appropriate conductor size and material to prevent excessive voltage drops and energy losses.
• Durability and Longevity: The selected cable should be robust and designed to last for the expected lifespan of the lighting installation. This minimizes maintenance and replacement costs over time.
• Compliance with Standards: The cable must adhere to relevant national and international standards, ensuring safety and reliability in operation.

Why this Option is Correct: In outdoor public lighting installations, cables must perform safely and reliably in challenging environmental conditions while meeting the electrical demands of the lighting fixtures. Option 2 captures these critical requirements, making it the correct choice.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Ignoring voltage drop calculations to reduce costs.

This option is incorrect because ignoring voltage drop calculations can lead to significant problems, such as insufficient power reaching the lighting fixtures, reduced efficiency, and potential damage to the equipment. Voltage drop calculations are essential to ensure the cables can deliver the required voltage to the lighting fixtures over long distances.

Option 3: Selecting the cheapest cable available.

This option is incorrect as it prioritizes cost over safety and performance. While cost considerations are important, selecting the cheapest cable without considering its suitability for the application can lead to safety hazards, reduced lifespan, and increased maintenance costs. Proper cable selection balances cost with performance, durability, and compliance with safety standards.

Option 4: The colour of the cable insulation.

This option is incorrect because the colour of the cable insulation is not a critical factor in its selection for outdoor public lighting installations. While insulation colour may have specific uses (e.g., identifying different circuits), it does not influence the cable's performance or ability to withstand environmental conditions and carry the required current.

Option 5: Not provided in the given data.

Since the data does not specify an Option 5, it is not relevant to the analysis of the correct answer.

Conclusion:

The correct answer, Option 2, highlights the critical factors in selecting cables for outdoor public lighting installations, focusing on their ability to withstand environmental conditions and carry the required current safely. This ensures the safety, reliability, and efficiency of the lighting system while adhering to necessary standards and minimizing long-term costs. Careful consideration of these factors is essential in achieving a successful and durable lighting installation.

Key Consideration When Designing an Electrical Installation Scheme for a Factory

Definition: When designing an electrical installation scheme for a factory, the foremost consideration is ensuring the safety, reliability, and functionality of the system. The correct option states that providing adequate protection against overloads, short circuits, and earth faults is a key requirement. This is essential because industrial environments typically involve complex electrical systems with high power demands, and any failure can lead to hazardous conditions, equipment damage, or operational disruptions.

Importance of Electrical Protection:

Electrical protection systems are vital for ensuring the safety of both equipment and personnel in a factory. Without adequate protection, the electrical system could be prone to faults such as overloads, short circuits, and earth faults, which can have severe consequences:

• Overloads: These occur when the current flowing through a circuit exceeds its designed capacity. Prolonged overloads can cause overheating, leading to insulation failure and potential fire hazards.
• Short Circuits: A short circuit happens when there is an unintended connection between two points of different potential, resulting in a sudden surge of current. This can cause extensive damage to equipment and create safety hazards.
• Earth Faults: These occur when a live conductor comes into contact with the earth or any conductive part that is not meant to carry current. Earth faults can lead to electric shock hazards and equipment damage.

Protective Devices Used in Factories:

To safeguard against these faults, various protective devices are employed in factory electrical systems, including:

• Circuit Breakers: These devices automatically disconnect a circuit when an overload or short circuit is detected. They are essential for preventing damage to equipment and ensuring the safety of personnel.
• Fuses: Fuses are simple, cost-effective devices that protect against overloads and short circuits by melting and disconnecting the circuit when excessive current flows.
• Residual Current Devices (RCDs): RCDs provide protection against earth faults by detecting leakage currents and disconnecting the circuit to prevent electric shock.
• Overload Relays: These are used to protect motors and other equipment from overload conditions by interrupting the circuit when the current exceeds a pre-set limit.

Designing a Safe and Reliable Electrical System:

When designing an electrical installation scheme, the following factors must be considered:

• Load Analysis: Assess the power requirements of all equipment and machinery to determine the total load and ensure the system is adequately sized.
• Proper Sizing of Conductors: Use conductors with appropriate cross-sectional areas to handle the expected current without overheating.
• Earthing System: Implement an effective earthing system to provide a low-resistance path for fault currents, ensuring the safety of personnel and equipment.
• Coordination of Protective Devices: Ensure that protective devices are properly coordinated to isolate faults without disrupting unaffected parts of the system.
• Compliance with Standards: Follow relevant electrical codes and standards to ensure the system meets safety and performance requirements.

Benefits of Adequate Protection:

Providing adequate protection against overloads, short circuits, and earth faults offers several benefits:

• Enhances the safety of personnel by reducing the risk of electric shock and fire hazards.
• Prevents damage to expensive equipment and machinery, reducing downtime and maintenance costs.
• Ensures the reliability and continuity of operations, minimizing production losses due to electrical faults.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: Minimising the use of protective devices to reduce costs

This option is incorrect because minimizing the use of protective devices compromises the safety and reliability of the electrical system. While cost considerations are important, they should never take precedence over safety. A lack of adequate protective devices can lead to catastrophic failures, endangering lives and causing significant financial losses.

Option 3: Focusing only on lighting and ventilation systems

This option is also incorrect. While lighting and ventilation systems are important components of a factory's electrical system, they are not the only aspects to consider. A comprehensive electrical installation scheme must address all power demands, including machinery, equipment, and auxiliary systems, to ensure the factory operates efficiently and safely.

Option 4: Ensuring the system is aesthetically pleasing

This option is not a key consideration for factory electrical systems. While aesthetics might be a factor in residential or commercial settings, the primary focus in industrial environments is on safety, functionality, and reliability. The appearance of the system is secondary to its performance and compliance with safety standards.

Conclusion:

In conclusion, the key consideration when designing an electrical installation scheme for a factory is ensuring adequate protection against overloads, short circuits, and earth faults. This is essential for safeguarding personnel, equipment, and operations. While cost, aesthetics, and specific systems like lighting and ventilation are important, they must not overshadow the primary goal of creating a safe and reliable electrical system. By prioritizing safety and adhering to best practices and standards, factories can achieve efficient and uninterrupted operations while minimizing risks and hazards.

The correct answer is option 3.

Specular reflection: The reflection of light from a smooth and shiny surface like a mirror is called specular reflection.

Key Characteristics:

• Occurs on smooth surfaces (e.g., mirrors, calm water).
• Light rays reflect in a single, predictable direction.
• Follows the law of reflection: the angle of incidence equals the angle of reflection.
• Produces clear images, like your reflection in a mirror.

Additional Information 

Other types of reflection are:
Spread reflection: Spread reflection, also known as diffuse or mixed reflection, occurs when light is reflected in a wide range of directions from a surface with imperfections, such as a rough surface or an uneven material. 
Irregular reflection: When a beam of light falls on such a surface which is not perfectly smooth and polished, such as a wall, wood paper etc. is known as irregular reflection.

Diffuse reflection: Diffuse reflection is the reflection of light from a surface such that an incident ray is reflected at many angles, rather than at just one angle as in the case of specular reflection.

Concept:

Electronic ballasts are advanced devices used in Compact Fluorescent Lamps (CFLs) to regulate the current and start the lamp quickly and efficiently. Unlike conventional magnetic ballasts, electronic ballasts operate at high frequencies (typically 20–60 kHz), which helps in eliminating visible flicker and delays during startup.

Benefits of Electronic Ballasts:

- Eliminate slow starting
- Eliminate flickering
- Improve energy efficiency
- Reduce humming noise and heat losses

Evaluation of Options:

Option 1: slow starting and flickering –  Correct
This is the main advantage of using electronic ballasts in CFLs.

The derived SI unit of illuminance is the lux (lx).

Luminous efficiency: It is also known as radiant efficiency. It is defined as the ratio of energy radiated in the form of light, produces sensation of vision to the total energy radiated out by the luminous body.

Radiant efficiency = energy radiated in the form of light / total energy radiated by the body

Lamp efficiency is measured in lumen/watt.

Important Points:

• Space to height ratio is the ratio of space between luminaires (S) to their height above the working plane (Hm).
• Manufacturers specify the recommended space to height ratio (SHR) for each of their luminaires.
• Typically, a recommended space to height ratio (SHR) is 1 : 2.

Concept:

Illumination is defined as the luminous flux received by the surface per unit area.

It is usually denoted by the symbol ‘E’ and is measured in lux or lumen/m² or meter candle or foot candle.

Illumination, \(E = \frac{\phi }{A} = \frac{{CP \times \omega }}{A}lux\)

Solid angle \(\omega = \frac{A}{{{d^2}}}\)

Illumination \(E = \frac{{CP}}{{{d^2}}}lux\)

Calculation:

Given that, candle power (CP) = 60 CP

Illumination (E) = 15 lux

⇒ 15 = 60/d²

⇒ d = 2 metres

The correct answer is option 4.

Sodium vapor lamps are also commonly used for sporting events, as they have a very high lumen-to-watt ratio typically 80–140 lumens/watt.

Applications of different types of lamps

Concept:

Illumination is defined as the luminous flux received by the surface per unit area.

It is usually denoted by the symbol ‘E’ and is measured in lux or lumen/m2 or meter candle or foot candle.

Illumination, \(E = \frac{\phi }{A} = \frac{{CP \times \omega }}{A}lux\)

Solid angle \(\omega = \frac{A}{{{d^2}}}\)

Illumination \(E = \frac{{CP}}{{{d^2}}}lux\)

Calculation:

Given that,

Illuminance = 64 π 

\(E= \frac{P}{4\pi r^2}=\frac{64\pi}{4\pi(4)^2}= 1\;lux\)

Definition of illumination (E):

illumination is defined as luminous flux received by the surface per unit area. Its unit is Lux or meter-candle or lumens per m²

Therefore,

illumination (E) = Lumen/area

\(=\frac{c.p\ \times\ ω}{A}\)

Where,

c.p = candle power

ω = solid angle = area/ d²

d = distance between the area and the point where the solid angle is formed

A = Area of cross-section

Applications are shown below: 

Concept:

Types of illumination

1.) Direct illumination

• In a direct scheme, about 90 % to 100 % of the total light flux or lumen is made to fall downward directly with the help of deep deflectors.
• This illumination has the highest efficiency but the brightness.
• This scheme is used for industrial purposes (factory lighting), street lamp lighting, and general outdoor lighting.

2.) Indirect illumination

• In an indirect scheme, more than 90 % of the total light flux or lumen is made thrown upward to the ceilings for diffuse reflection.
• This scheme of lighting is achieved by using inverted or bowl-shaped reflectors.
• This type of scheme is mostly used for decoration purposes in places like cinema halls, theaters, and hotels.

3.) Semi-direct illumination

• In a semi-direct scheme, about 60 % to 90 % of the total light flux or lumen is made to fall with the help of semi-direct reflectors.
• The remaining percentage of the light is used to illuminate the ceilings and walls.
• This type of scheme is best suited for rooms with high ceilings.

4.) Semi-indirect illumination

• In a semi-indirect scheme, about 60 % to 90 % of the total light flux or lumen is thrown directly upwards to the ceilings for the defused reflection.
• The remaining amount of light reaches the working plane directly except those absorbed by the fixtures.
• This type of scheme is used for decoration purposes.

Luminous Intensity (candela - cd): Luminous intensity is a measure of the amount of light emitted by a source in a particular direction. The unit of luminous intensity is the candela (cd).

Luminous Flux (lumen - lm): Luminous flux is the total amount of visible light emitted by a source, regardless of direction. The unit of luminous flux is the lumen (lm).

Illuminance (lux - lx): Illuminance is the amount of light falling on a surface per unit area. The unit of illuminance is the lux (lx), and it is measured in lumens per square meter.

Luminance (candela per square meter - cd/m²): Luminance is the measure of the brightness of a surface as perceived by an observer. It takes into account the intensity of the light emitted or reflected by the surface and the angle at which it is viewed. Luminance is measured in candelas per square meter (cd/m²).

In summary, candela per square meter (cd/m²) is specifically the unit used to measure luminance, which considers the intensity of light from a surface as perceived by an observer

Methods for calculating the Illumination of Light

The three main methods are as follows:

1.) Watt per Square Meter Method

• The watt-per-square meter method is fundamentally a rule-of-thumb method. 
• This method is used for rough calculations and checking purposes.
•  It entails allocating watts per square meter of the area to be illuminated in accordance with the desired illumination, based on an average figure of overall system efficiency.

2.) Lumen Method

• The lumen method is also called the light flux method.
• It is the method employed for lighting calculation that is applicable to those cases where the sources of light are such as to produce an approximate uniform illumination over the working plane or where an average value is required.

3.) Inverse Square Law Method

• The inverse square law method is also known as a point-to-point method.
• It is applicable where illumination at a point due to one or more sources of light is required. Though, the candle power of the sources in the particular direction under consideration is known.