ITI Electronics Mechanic Viva Questions and Answers
In the electronics mechanic practical, you build or repair a circuit, take readings, and then the examiner asks you to explain what you did. These are the questions asked most often, with short answers you can say in the viva.
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A working circuit with clean solder joints, the right component in the right place and correct readings on the meter or CRO. Then your knowledge of components, power supplies, digital circuits and safety.
Electronics mechanic viva questions with answers
Components
How do you read the value of a resistor from its colour bands?
The first two bands are digits and the third is the multiplier. Black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. A gold fourth band means ±5% tolerance and silver means ±10%. Brown, black, red is 10 × 100 = 1 kΩ.
How to say it: Read one resistor from your own board aloud.
How do you find the positive leg of an electrolytic capacitor and an LED?
On an electrolytic capacitor the longer leg is positive and the negative side is marked with a stripe. On a new LED the longer leg is the anode (positive), and the flat edge on the body marks the cathode.
What is the forward voltage drop of a silicon diode?
About 0.7 V. A germanium diode drops about 0.3 V.
Where is a zener diode used?
As a voltage regulator. It is connected in reverse bias and holds the voltage across it close to its zener voltage.
What are the terminals of a transistor, and what are the two types?
Emitter, base and collector. The two types are NPN and PNP. In an NPN transistor the arrow on the emitter points outward.
Power supply
What is a rectifier, and what are its types?
A circuit that changes AC into DC. Half wave uses one diode, full wave centre tap uses two diodes with a centre-tapped transformer, and the bridge rectifier uses four diodes.
Why is a capacitor connected after the rectifier?
It is a filter. It charges on the peaks and discharges between them, so the pulsating DC becomes smoother.
What does a 7805 IC do?
It is a fixed voltage regulator that gives a steady +5 V output. 7812 gives +12 V; the 79xx series gives negative voltages.
How do you test a diode with a multimeter?
Put the meter on the diode range. With red on the anode and black on the cathode it shows a forward drop (about 0.6 to 0.7 V for silicon). Reversed, it shows OL. A reading both ways means the diode is short; OL both ways means it is open.
Digital and ICs
Which gates are called universal gates, and why?
NAND and NOR, because any other gate can be built using only NAND gates or only NOR gates.
What are the three modes of a 555 timer?
Astable (free-running, gives a square wave), monostable (one pulse for each trigger) and bistable (flip-flop).
What is the output of an AND gate and an OR gate?
An AND gate gives 1 only when all inputs are 1. An OR gate gives 1 when any input is 1.
What do you measure with a CRO?
The shape of a waveform, its peak voltage, its time period and from that its frequency (f = 1 / T).
Soldering and safety
What makes a good solder joint?
A shiny, smooth, cone-shaped joint that wets both the pad and the lead. A dull, ball-shaped joint is a dry joint and may not conduct.
Why is flux used in soldering?
It cleans the oxide from the metal surfaces so the solder flows and sticks.
Why do you wear an anti-static wrist strap?
Static charge from the body can damage ICs and MOSFETs. The strap drains that charge to earth.
What safety do you follow while working on a circuit?
Switch off and unplug before touching the circuit, discharge large capacitors, keep the soldering iron in its stand and use the correct meter range before measuring.
Your opening answer to practise
Copy the lines that are true for you, replace every [bracket] and delete the rest. Every number should be one you can repeat in a practical test.
Opening answer for the Electronics Mechanic viva
- My name is [name], roll number [number], trainee of ITI Electronics Mechanic, [ITI name], session [year].
- Today my practical job was [e.g. assembling and testing a bridge rectifier with a filter capacitor].
- I followed the safety steps: [power off while wiring, iron in its stand, wrist strap worn].
- The result: [e.g. about 12 V DC output measured on the multimeter].
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Common questions
What questions are asked in the ITI electronics mechanic viva?
Resistor colour code, capacitor and LED polarity, diodes and zener diodes, transistor terminals, rectifiers and filters, 7805 regulator, logic gates, the 555 timer, CRO readings, soldering and safety, plus questions on the circuit you made.
Which question is asked most often?
Reading a resistor from its colour bands, and how a bridge rectifier works.
Will the examiner check my circuit?
Usually yes. Be ready to show where you measured, what the reading was and why it matches the expected value.
Can I get these viva questions as a PDF?
Open the page, choose Print in your browser menu, then Save as PDF. The page prints without menus.
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