Assam HS Skill Electrical Mechanics and Electrician common mistakes
Assam HS Skill Electrical Mechanics and Electrician · Understand the traps and how to avoid them.
When asked to compute current, voltage, or resistance, the candidate substitutes values into V = IR or P = VI without first converting mixed prefixes (mA, kΩ, MΩ, kW) to base units, and writes an answer like 'I = 0.5' with no unit or with the wrong magnitude.
In the viva and numerical items, values are deliberately given in mixed prefixes to test practical fluency. Candidates memorise the formula triangle but practise only with whole numbers, so the prefix conversion step is skipped under time pressure, and the missing unit hides the error from self-checking.
What to do instead
Adopt a fixed three-line working habit: (1) rewrite every given quantity with its prefix expanded to base units before touching a formula, (2) solve, (3) attach and sanity-check the unit (e.g. a 230 V lamp of 1 kΩ must draw about 0.23 A, not 230 A). Practise ten mixed-prefix problems per session until the conversion line appears automatically.
The candidate wires a two-way staircase circuit or a socket outlet from memory without following a wiring diagram, then cannot explain at viva why the lamp stays on in both switch positions or why the earth pin is connected where it is.
Wiring is learned by copying a demonstrator's hand movements rather than by reading the schematic. Because the candidate never maps diagram symbols to physical terminals, small transpositions (common terminal versus L1/L2, live and earth swapped at the socket) go unnoticed and the circuit 'works' only by coincidence or not at all.
What to do instead
Before touching a conductor, redraw the circuit from the given diagram in the candidate's own hand and label every terminal (L, N, E, COM, L1, L2). Then wire strictly terminal by terminal, ticking each label off. After wiring, trace continuity with a multimeter and state aloud what each reading should be before measuring it.
On a straight-through or T-joint, the candidate twists the conductors together and tapes them, or makes the joint but leaves a sharp wire end protruding, and does not insulate with the prescribed layers.
The candidate confuses a mechanically twisted temporary connection with a proper joint. Time pressure in the practical slot encourages a quick twist, and the habit persists because the joint is never pull-tested or inspected against a standard.
What to do instead
Practise each joint type (straight-through, T, western union, married) to a fixed sequence: correct strip length, clean bare conductor, tight mechanical turns in the specified direction, solder or crimp as required, then insulation in the prescribed layers with no exposed conductor. Finish every joint with a firm pull test and a visual check for stray strands before presenting it.
When asked about a transformer's losses, efficiency, or why a transformer cannot work on DC, the candidate recites 'eddy current and hysteresis' as a phrase but cannot say where each loss occurs, how it varies with load, or what happens physically if DC is applied.
Transformer theory is memorised as a list of keywords from a summary sheet rather than understood as a magnetic-circuit argument. The candidate has never reasoned from flux, frequency, and induced EMF, so any question phrased differently from the textbook sentence defeats them.
What to do instead
Build the explanation from first principles in writing: core loss is constant and lives in the iron (hysteresis from reversals, eddy currents from circulating paths, reduced by laminations), copper loss is I²R and varies with load squared. For DC, state that flux is steady, so no induced back-EMF arises, current is limited only by small winding resistance, and the winding overheats. Rehearse this as a two-minute spoken answer.
The candidate connects a wattmeter, energy meter, or multimeter without checking polarity, range, or the correct terminals (current coil in series, voltage coil in parallel), and reads an analogue scale using the wrong multiplying factor or the wrong arc.
Instrument connection is taught as a picture to copy, not as a circuit decision. Candidates also neglect to select the range before energising and read the nearest number on the scale without computing the factor from full-scale deflection and range selected.
What to do instead
Use a pre-connection checklist every time: identify the instrument, confirm the range covers the expected value, verify terminal markings (line/load, +/-, COM), connect the current path in series and the voltage path in parallel, then energise. For analogue meters, calculate the reading as (indicated divisions ÷ full-scale divisions) × range before stating the answer.
The candidate describes earthing as 'connecting to the ground' and cannot distinguish earth wire, neutral, and body earth, nor state the purpose and typical resistance value of a protective earth, and treats a fuse and an MCB as interchangeable without explaining their difference.
Safety topics are skimmed as general awareness rather than examined as technical content. Candidates learn the words 'earthing protects us' without linking touch voltage, fault current path, and the opening of the protective device.
What to do instead
Write a one-page fault-path sketch: source, live conductor, faulty appliance body, earth conductor, earth electrode, back to source, and mark where the fuse or MCB operates. Learn the standard earth-resistance expectation and the meaning of touch and step potential. Then tabulate fuse versus MCB on operating principle, resetability, breaking capacity, and response time, and rehearse each aloud.
Given a small installation to estimate, the candidate totals only the cost of lamps and switches, omitting conduit, accessories, labour, wastage, and overheads, and presents the figure without a take-off sheet or rate justification.
Estimation is treated as arithmetic on a shopping list rather than as a measurement-and-rate exercise. The candidate has not seen a real bill of quantities, so labour, wastage percentages, and overheads are invisible to them.
What to do instead
Always start from a measured take-off: count and measure each item, apply a stated wastage allowance, then price materials, labour, and overheads in separate columns. Show the rate assumed for each line so the examiner can follow the reasoning, and finish with a summary total. Practise one complete small estimate per week using a standard schedule-of-rates format.
When explaining a rectifier, transistor switch, or thyristor control, the candidate names the component but cannot describe the current path, the role of the diode in a half-wave or bridge rectifier, or why a thyristor needs a gate pulse to conduct.
Industrial electronics is studied as component identification rather than as circuit behaviour. Without tracing current through each half-cycle, the candidate has no model to reason from and falls back on labels.
What to do instead
For each circuit, draw the waveform and mark which devices conduct in each half-cycle, then explain the output in words. For the thyristor, state explicitly that forward voltage alone will not start conduction and that gate triggering latches it on until current falls below holding level. Rehearse by teaching the circuit to a peer without notes.
In appliance repair, the candidate immediately opens the appliance and starts replacing parts, or tests a suspected live circuit with a multimeter set to the wrong function, without first isolating supply, confirming dead, and asking the customer what the symptom was.
Practical slots reward speed, and fault-finding is confused with part-swapping. Candidates also lack a safe isolation routine, so the dead-test step is skipped and diagnostic reasoning is replaced by guesswork.
What to do instead
Follow a fixed sequence every time: interview the user for the symptom, isolate and lock off, prove dead with a tested instrument, then diagnose by half-split testing (supply, switch, element, continuity) and record findings before replacing anything. State the safe-isolation steps aloud during the viva so the examiner sees the discipline.
During the viva, the candidate answers in one-word fragments, cannot explain the purpose of a tool they have just used, and does not connect the practical task to the underlying principle (for example, why a megger is used instead of a multimeter for insulation resistance).
Practical skill is developed without verbal rehearsal, so the candidate performs correctly but cannot articulate the reason. Under viva pressure they answer the literal question only and do not volunteer the principle the examiner is probing for.
What to do instead
After every workshop task, write and speak a short justification: what was done, which instrument or tool was used, why that one rather than an alternative, and what the reading proves. Practise answering in a three-part structure (statement, reason, safety implication) and have a peer ask follow-up 'why' questions until the explanation holds.