RRB ALP Electronics Mechanic Trade — Solved Practice Question Bank

Q: A resistor has color bands Brown-Black-Red-Gold. Find its resistance and tolerance. Sol: Brown=1, Black=0, Red=multiplier ×100; so value = 10×100 = 1000Ω = 1kΩ; Gold = ±5% tolerance. Q: Why must an electrolytic capacitor be connected with correct polarity? Sol: It is a polarized component — reverse-polarity connection can damage the dielectric layer, causing overheating, leakage, or even explosive failure. Q: Which two logic gates are called "universal gates"? Sol: NAND and NOR — either one alone can be used to construct any other logic gate/function.

Q: What does a dull, grainy appearance of a solder joint usually indicate? Sol: A "cold" solder joint — caused by insufficient heat or time during soldering, resulting in a poor, unreliable electrical/mechanical connection. Q: Which instrument is used to observe the shape and frequency of an electrical waveform? Sol: A Cathode Ray Oscilloscope (CRO). Q: What is the purpose of a solder wick in electronics repair? Sol: To desolder a joint — it absorbs molten solder via capillary action when heated with a soldering iron, allowing a component to be removed cleanly.