SECTIONA. Answer ALL the questions in this Section. ( 40 marks) 1. Name two types or classifications of Dc machines (2mks) 2. Name four parts of DC machines (4mks) 3. Identify any four types of electrical machines that you I know. (4mks) 4. State Four of the protective or control devices used in motor installation (4mks) 5. Outline some four motor starting methods which are generally used in industries (4mks) 6. State the differences between a three phase motor and a single phase motor (2mks) 7. Highlight two differences between stator and a rotor (2mks) 8.Highlight two ways through which a single phase motor can be made to self- start (4mks) 9. Define term power factor (2mks) 10. Define the following: i). Reactive power ii). Useful power iii. Apparent power (6mks) 11. Draw and name simple diagram of a single phase transformer (4mks) 12. Briefly explain how transformer works (4mks) 13. State faradays laws of electromagnetic induction

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SECTIONA. Answer ALL the questions in this Section. ( 40 marks) 1. Name two types or classifications of Dc machines (2mks) 2. Name four parts of DC machines (4mks) 3. Identify any four types of electrical machines that you I know. (4mks) 4. State Four of the protective or control devices used in motor installation (4mks) 5. Outline some four motor starting methods which are generally used in industries (4mks) 6. State the differences between a three phase motor and a single phase motor (2mks) 7. Highlight two differences between stator and a rotor (2mks) 8.Highlight two ways through which a single phase motor can be made to self- start (4mks) 9. Define term power factor (2mks) 10. Define the following: i). Reactive power ii). Useful power iii. Apparent power (6mks) 11. Draw and name simple diagram of a single phase transformer (4mks) 12. Briefly explain how transformer works (4mks) 13. State faradays laws of electromagnetic induction

Answer 1

1. Two types or classifications of DC machines are: - Generators - Motors2. Four parts of DC machines are: - Stator - Rotor - Commutator - Brushes3. Four types of electrical machines are: - Transformers - Generators - Motors - Inductors4. Four protective or control devices used in motor installation are: - Circuit breakers - Fuses - Overload relays - Temperature sensors5. Four motor starting methods generally used in industries are: - Direct on-line starting - Star-delta starting - Autotransformer starting - Soft starting6. Differences between a three-phase motor and a single-phase motor: - Three-phase motors have three windings and operate on three-phase power, while single-phase motors have one winding and operate on single-phase power. - Three-phase motors have a more constant torque and smoother operation compared to single-phase motors.7. Two differences between a stator and a rotor: - The stator is the stationary part of an electric machine, while the rotor is the rotating part. - The stator is typically the outer frame of the machine, while the rotor is located inside the stator.8. Two ways to make a single-phase motor self-start: - Using a centrifugal switch - Using a phase-shifting capacitor9. Power factor is the ratio of real power (active power) to apparent power in an AC circuit.10. Definitions: i) Reactive power: The imaginary component of electrical power, measured in VARs (Volt-Ampere Reactive). ii) Useful power: The real power that performs useful work in an electrical circuit, measured in watts (W). iii) Apparent power: The total power in an AC circuit, measured in volt-amperes (VA), which includes both real power and reactive power.11. Diagram of a single-phase transformer:![Single-Phase Transformer Diagram](https://i.imgur.com/5vZqfLk.png)12. A transformer works by using electromagnetic induction to transfer electrical energy between two or more coils of wire. When an AC voltage is applied to the primary coil, it creates a magnetic field that induces a voltage in the secondary coil.13. Faraday's laws of electromagnetic induction: - The induced electromotive force (EMF) in a closed circuit is proportional to the rate of change of the magnetic flux through the circuit. - The direction of the induced EMF is such that it opposes the change in magnetic flux that produced it.

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