MOTORS, GENERATORS AND TRANSFORMERS

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• Q1: What is Faraday’s First Law?
  Ans: Faraday’s First Law of Electromagnetic Induction states that when the magnetic flux linked with a conductor changes, an electromotive force (EMF) is induced in it.
• Q2: What is Faraday’s Second Law?
  Ans: Faraday’s Second Law states that the magnitude of induced EMF is directly proportional to the rate of change of magnetic flux.
• Q3: What is a D.C Machine?
  Ans: A D.C machine is an electrical machine that works on direct current (DC). It can convert electrical energy into mechanical energy or mechanical energy into electrical energy.
• Q4: What is a Generator?
  Ans: A generator is a machine that converts mechanical energy into electrical energy based on the principle of electromagnetic induction.
• Q5: What is an Elementary DC Generator?
  Ans: An elementary DC generator is a simple form of DC generator used to explain the basic working principle of converting mechanical energy into DC electrical energy.
• Q6: What are Sloit rings used for?
  Ans: Slot rings (Slip rings) are used to transfer electrical current between a stationary and a rotating part of a machine without twisting wires.
• Q7: Define Pulsating.
  Ans: Pulsating means a current or voltage that varies in magnitude with time but does not completely change its direction.
• Q8: State the main parts of a D.C Machine.
  Ans: The main parts of a D.C machine are:

  • ➔ Yoke
  • ➔ Poles
  • ➔ Field Windings
  • ➔ Armature
  • ➔ Commutator
  • ➔ Brushes
  • ➔ Bearings
• Q9: What is a Yoke? What is it used for?
  Ans: A yoke is the outer frame of a D.C machine.
  It is used to:

  • ➔ Provide mechanical support to the machine
  • ➔ Protect the internal parts
  • ➔ Carry magnetic flux
• Q10: What is a Commutator?
  Ans: A commutator is a mechanical device used in D.C machines that converts alternating current (AC) induced in the armature into direct current (DC).
• Q11: What is an Armature Coil?
  Ans: An armature coil is a conductor winding placed on the armature of a D.C machine where EMF is induced.
• Q12: What is Eddy’s Current?
  Ans: Eddy currents are circulating currents induced in a conductor when it is placed in a changing magnetic field. These currents cause energy loss in the form of heat.
• Q13: What is a Rocker?
  Ans: A rocker is a part of a D.C machine that holds the brushes in position and allows adjustment for proper contact with the commutator.
• Q14: What are Bearings??
  Ans: Bearings are mechanical parts that support the rotating shaft of a machine and reduce friction during rotation.
• Q15: What is a D.C Motor?
  Ans: A D.C motor is an electrical machine that converts electrical energy into mechanical energy using direct current.
• Q16: Briefly explain the working principle of a D.C Motor.
  Ans: A D.C motor works on the principle that a current-carrying conductor placed in a magnetic field experiences a mechanical force.
  This force causes the conductor (armature) to rotate, producing mechanical motion.
• Q17: What is Fleming;s Left Hand Rule?
  Ans: Fleming’s Left Hand Rule states that if the thumb, forefinger, and middle finger of the left hand are stretched mutually perpendicular, then:
  

  • ➔ Forefinger shows magnetic field direction
  • ➔ Middle finger shows current direction
  • ➔ Thumb shows force (motion) direction
• Q18: What is a Stepper Motor?
  Ans: A stepper motor is an electric motor that moves in small, fixed steps instead of continuous rotation. It is used for precise position control.
• Q19: Briefly explain the working of a Stepper Motor.
  Ans: A stepper motor works by energizing its coils in a specific sequence.
  Each pulse of current rotates the motor by a fixed angle called a step, allowing precise control of position.
• Q20: State four advantages of Stepper Motor.
  Ans: Advantages of stepper motor:

  • ➔ High precision positioning
  • ➔ Simple control system
  • ➔ No feedback system required
  • ➔ Good holding torque at standstill
• Q21: State four disadvantages of Stepper Motor.
  Ans: Disadvantages of stepper motor:

  • ➔ Low efficiency at high speeds
  • ➔ Can lose steps under heavy load
  • ➔ Produces vibration and noise
  • ➔ Limited torque at high speed
• Q22: State four uses of Stepper Motor.
  Ans: Uses of stepper motor:

  • ➔ Printers and scanners
  • ➔ CNC machines
  • ➔ Robotics
  • ➔ Camera positioning systems
• Q23: What is a Servo Motor?
  Ans: A servo motor is a special type of motor used for precise control of position, speed, and angle. It works with a feedback system to achieve accurate movement.
• Q24: State the types of Servo Motor.
  Ans: The types of servo motors are:

  • ➔ AC Servo Motor
  • ➔ DC Servo Motor
• Q25: What is a D.C Servo Motor?
  Ans: A D.C servo motor is a servo motor that operates on direct current (DC) and is used for precise control of angular position and speed.
• Q26: What is an A.C Servo Motor?
  Ans: An A.C servo motor is a servo motor that operates on alternating current (AC) and is used in high-speed and high-precision control applications.
• Q27: What is an A.C Generator?
  Ans: An A.C generator (alternator) is a machine that converts mechanical energy into alternating electrical energy using electromagnetic induction.
• Q28: What is an Induction Motor?
  Ans: An induction motor is an AC electric motor in which current is produced in the rotor by electromagnetic induction instead of direct electrical connection.
• Q29: State the uses of Induction Motor.
  Ans: Uses of induction motor:

  • ➔ Fans and blowers
  • ➔ Water pumps
  • ➔ Conveyor systems
  • ➔ Industrial machines
• Q30: Briefly explain the working of an Induction Motor.
  Ans: An induction motor works on the principle of electromagnetic induction.
  When AC supply is given to the stator, it produces a rotating magnetic field.
  This induces current in the rotor, and interaction between magnetic fields produces torque, causing rotation.
• Q31: What is a Stator?
  Ans: The stator is the stationary part of an electrical machine that produces a magnetic field.
• Q32: What is a Rotor?
  Ans: The rotor is the rotating part of an electrical machine that rotates due to electromagnetic interaction with the stator field.
• Q33: What is a Transformer?
  Ans: A transformer is an electrical device that transfers electrical energy from one circuit to another through electromagnetic induction without changing frequency.
• Q34: State four uses of the transformer.
  Ans: Uses of transformer:

  • ➔ Voltage step-up and step-down in power systems
  • ➔ Power transmission and distribution
  • ➔ Electrical isolation
  • ➔ Electronic devices and chargers
• Q35: State the types of Transformers.
  Ans: Types of transformers:

  • ➔ Step-up transformer
  • ➔ Step-down transformer
  • ➔ Core type transformer
  • ➔ Shell type transformer
• Q36: Name the parts of the transformer.
  Ans: Parts of transformer:

  • ➔ Core
  • ➔ Primary winding
  • ➔ Secondary winding
  • ➔ Insulation
  • ➔ Transformer tank
  • ➔ Oil (for cooling)
• Q37: What is a Step-up transformer?
  Ans: A step-up transformer increases the voltage from primary side to secondary side and decreases the current.
• Q38: What is a Step-down Transformer?
  Ans: A step-down transformer decreases the voltage from primary side to secondary side and increases the current.
• Q39: Write the working principle of a transformer.
  Ans: A transformer works on the principle of electromagnetic induction.
  A changing current in the primary coil produces a changing magnetic flux, which induces EMF in the secondary coil.
• Q40: What is a Breather?
  Ans: A breather is a device used in transformers to absorb moisture from air entering the transformer, usually containing silica gel.
• Q41: What is a Core Type Transformer?
  Ans: A core type transformer is one in which the windings are placed on two limbs of a rectangular magnetic core.
• Q42: What is a Shell Type Transformer?
  Ans: A shell type transformer is one in which the core surrounds the windings, providing better magnetic protection.
• Q43: Write the EMF equation for the transformer.
  Ans: The EMF equation of a transformer is:
  E₂ / E₁ = N₂ / N₁
  Where:
  E = induced EMF
  N = number of turns
• Q44: What is a Welding Transformer?
  Ans: A welding transformer is a step-down transformer used to provide low voltage and high current required for welding purposes.
• Q45: Define Flux.
  Ans: Magnetic flux is the total number of magnetic field lines passing through a given area.
• Q46: What is an Alternator?
  Ans: An alternator is a machine that converts mechanical energy into alternating current (AC) electrical energy.
• Q47: Name the parts of an Alternator.
  Ans: Parts of an alternator:

  • ➔ Stator
  • ➔ Rotor
  • ➔ Slip rings
  • ➔ Brushes
  • ➔ Shaft
• Q48: What is Field Wiring?
  Ans: Field winding is the winding in electrical machines that produces the main magnetic field when current passes through it.
• Q49: What is a 3 phase Induction Motor?
  Ans: A 3 phase induction motor is an AC motor that runs on three-phase supply and produces a rotating magnetic field for operation.
• Q50: What is a Single phase Induction Motor?
  Ans: A single phase induction motor is an AC motor that runs on single-phase supply and is commonly used in small household appliances.