Essential Electrical Engineering Exam Questions and Answers
Essential Electrical Engineering Exam Q&A
Here are detailed answers in English for all questions (exam-ready) 📘✍️
Q1. Difference Between AC and DC Supply
AC (Alternating Current) Supply: Alternating current is the type of electrical supply in which the magnitude and direction of current change periodically with time. The waveform of AC is usually sinusoidal. AC is used for power transmission because it can be easily stepped up or stepped down using transformers.
Characteristics of AC
- Direction changes periodically
- Has frequency (50 Hz in India)
- Easily transmitted over long distances
- Can be stepped up/down using a transformer
- Example: Household electricity supply
DC (Direct Current) Supply: Direct current is the type of electrical supply in which the magnitude and direction of current remain constant. It flows only in one direction.
Characteristics of DC
- Flows in one direction only
- No frequency
- Cannot be transformed easily
- Used in electronic circuits
- Example: Battery, solar cell
Q2. Difference Between Analog and Digital Instruments
Analog Instruments: These display readings using a pointer moving over a scale. The deflection of the pointer indicates the measured value.
Advantages & Disadvantages
- Advantages: Simple construction, cheap.
- Disadvantages: Less accuracy, parallax error occurs, difficult to read.
Digital Instruments: These display readings in numeric form using a digital display such as LCD or LED.
Advantages & Disadvantages
- Advantages: High accuracy, easy to read, no parallax error, compact size.
- Disadvantages: Costly, requires power supply.
Q3. Digital Multimeter
A digital multimeter is an electronic measuring instrument used to measure voltage, current, and resistance. It combines the functions of a voltmeter, ammeter, and ohmmeter in a single device.
Functions and Applications
- Functions: Measurement of AC/DC voltage, current, resistance, continuity, and diode testing.
- Applications: Electrical maintenance, electronic circuit testing, laboratory measurement.
Q4. Various Joints Used in Electrical Systems
Electrical joints are used to connect two conductors mechanically and electrically.
- Straight Through Joint: Used to join two wires in a straight line.
- Tee Joint: Used when a branch connection is required.
- Western Union Joint: Strong joint used in overhead lines.
- Britannia Joint: Used for heavy current-carrying conductors.
- Married Joint: Used in flexible wire connections.
- Knotted Tap Joint: Provides a strong tapping connection.
Q5. Colour Coding of Resistors
Resistor values are represented by coloured bands. Each colour represents a number.
| Colour | Digit | Multiplier |
|---|---|---|
| Black | 0 | 10⁰ |
| Brown | 1 | 10¹ |
| Red | 2 | 10² |
| Orange | 3 | 10³ |
| Yellow | 4 | 10⁴ |
| Green | 5 | 10⁵ |
| Blue | 6 | 10⁶ |
| Violet | 7 | 10⁷ |
| Grey | 8 | 10⁸ |
| White | 9 | 10⁹ |
Tolerance: Gold = ±5%, Silver = ±10%
Q6. Colour Coding of Capacitors
Capacitors use colour coding to represent capacitance value: First band (digit) – Second band (digit) – Third band (multiplier in pF).
Q7. Finding Colour Code of Resistance
Example: 4.7 kΩ
4 (Yellow) – 7 (Violet) – Multiplier 10² (Red) – Tolerance (Gold).
Answer: Yellow – Violet – Red – Gold.
Q8. Common Electrical Symbols
- Resistor: Limits current
- Capacitor: Stores charge
- Inductor: Stores magnetic energy
- Battery: DC source
- Switch: Opens or closes circuit
- Ammeter/Voltmeter: Measures current/voltage
- Ground: Reference point
- Transformer: Steps voltage
- Fuse: Protection device
Q9. Definitions in Alternating Current
- Time Period (T): Time required to complete one full cycle.
- Cycle: One complete positive and negative alternation.
- Amplitude: Maximum value from zero level.
- Frequency (f): Cycles per second (f = 1/T, Unit: Hz).
- Peak Factor: Peak value / RMS value.
- Form Factor: RMS value / Average value.
- RMS Value: Effective value producing the same heating effect as DC (0.707 × Peak value).