NMDC Limited Junior Engineer Electrical Interview Questions and Answers

Information in electrical generation distribution working

Q1. Introduction and inquiry
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Q1. Define the term Capacitance and Inductance?
Ans. 
Capacitance is the ability of a body to store an electric charge. Inductance is the ability of a coil to store energy in a magnetic field.
• Capacitance is measured in Farads (F)

• Capacitors are used to store energy in electronic circuits

• Inductance is measured in Henrys (H)

• Inductors are used in electronic circuits to store energy in a magnetic field

• Both capacitance and inductance are important in AC circuits
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Q2. Mention what are the different kind of cables used for transmissions?
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Different types of cables used for transmissions include coaxial, twisted pair, fiber optic, and ribbon cables.
• Coaxial cables are used for high-frequency transmissions and have a copper core surrounded by insulation and a braided shield.

• Twisted pair cables are used for low-frequency transmissions and have two insulated copper wires twisted together.

• Fiber optic cables use light to transmit data and are made of glass or ...read more
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Aptitude, Reasoning, General Knowledge and Technical domain

Q1. Interview related to your technical domain.
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Q2. About yourself, your technical skills and expertise.
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Q1. How many layers in underground cable
Ans. 
Underground cables typically have multiple layers for insulation and protection.
• Underground cables usually have three layers: conductor, insulation, and protective sheath

• The conductor layer carries the electrical current

• The insulation layer prevents leakage of current and protects against environmental factors

• The protective sheath provides additional protection from moisture, chemicals, and physical damage
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Q1. What is transformer
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A transformer is a device that transfers electrical energy between two or more circuits through electromagnetic induction.
• Consists of two coils of wire (primary and secondary) wrapped around a core

• Primary coil receives electrical energy and creates a magnetic field

• Magnetic field induces a voltage in the secondary coil, transferring energy

• Used to step up or step down voltage in power distribution systems
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Q2. What is current transformer?
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A current transformer is a type of instrument transformer used to measure alternating current.
• Used to step down high currents to a lower, more manageable level for measurement

• Consists of a primary winding and a secondary winding

• Secondary winding is connected to measuring instruments or protective relays

• Provides accurate current measurement without affecting the main circuit
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Q3. What is the difference between ideal transformer and practical transformer?
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Ideal transformer is theoretical with no losses, while practical transformer has losses due to resistance, leakage flux, etc.
• Ideal transformer has no losses, while practical transformer has losses due to resistance, leakage flux, hysteresis, and eddy currents

• Ideal transformer has infinite efficiency, while practical transformer has efficiency less than 100%

• Ideal transformer has no voltage drop, while practical transfor...read more
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Q4. What is voltage?
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Voltage is the difference in electric potential between two points in a circuit, measured in volts.
• Voltage is the force that pushes electric current through a circuit.

• It is measured in volts (V).

• Higher voltage means more potential energy for electrons to flow.

• Voltage can be compared to water pressure in a pipe - higher pressure (voltage) means faster flow (current).
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Q5. What is turn ratio?
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Turn ratio is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding of a transformer.
• Turn ratio determines the voltage transformation ratio in a transformer.

• It is calculated by dividing the number of turns in the primary winding by the number of turns in the secondary winding.

• For example, if a transformer has 100 turns in the primary winding and 200 turns in the seconda
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Q6. What is the emf equation of transformer?
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The emf equation of a transformer relates the induced voltage to the number of turns in the primary and secondary coils.
• The emf equation of a transformer is given by: E = N*dΦ/dt, where E is the induced voltage, N is the number of turns, and dΦ/dt is the rate of change of magnetic flux.

• This equation shows that the induced voltage in a transformer is directly proportional to the number of turns in the coils and the rate...read more
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Q7. What is current?
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Current is the flow of electric charge in a circuit.
• Current is measured in Amperes (A).

• It is the rate of flow of electric charge past a point in a circuit.

• Current can be either direct current (DC) or alternating current (AC).

• Examples: A light bulb draws current from a power source to produce light. A fan motor requires current to spin.
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Q8. What is potential transformer
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A potential transformer is a type of instrument transformer used to step down high voltage to a lower, safer voltage for measurement or control purposes.
• Used to step down high voltage to a lower voltage for measurement or control purposes

• Provides accurate voltage measurements for meters and relays

• Commonly used in power systems for protection and metering applications
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Q9. What is inductance
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Inductance is the property of an electrical circuit that opposes changes in current flow.
• Inductance is measured in Henrys (H)

• It is caused by the magnetic field generated when current flows through a conductor

• Inductors are components that are designed to have a specific inductance value

• Inductance is used in circuits to store energy in the form of a magnetic field
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Q10. What is capacitance
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Capacitance is the ability of a system to store an electric charge.
• Capacitance is measured in farads (F).

• It is the ability of a capacitor to store energy in an electric field.

• Capacitance depends on the geometry of the capacitor and the dielectric material between the plates.

• Capacitance is calculated as C = Q/V, where C is capacitance, Q is charge, and V is voltage.
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Q11. What is unit of inductor
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The unit of inductor is Henry (H)
• The unit of inductor is named after American scientist Joseph Henry

• It is represented by the symbol 'H'

• 1 Henry is equal to 1 volt-second per ampere
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