Haryana BSEH Secondary NSQF Power common mistakes
Haryana BSEH Secondary NSQF Power · Understand the traps and how to avoid them.
When asked to size a fuse or MCB for a given load, the candidate picks a rating equal to or slightly below the calculated load current instead of selecting the next standard rating above it.
The candidate memorises 'fuse rating = current' as a formula and stops at the arithmetic, forgetting that a protective device must carry the normal load continuously without nuisance tripping, so the rating must exceed the design current and then match a standard value.
What to do instead
Always finish the calculation with two explicit steps: compute design current I = P/V (or kW×1000/230), then move up to the next standard device rating (6, 10, 16, 20, 25, 32, 40 A) and state the cable must have a current-carrying capacity at least equal to that rating. Practise five such selections and write the 'next standard size' line every time.
Treating earth (protective) conductor and neutral as interchangeable, or describing the earth wire as carrying current during normal operation.
The two wires look similar in diagrams and both are often shown connected at the supply transformer star point, so candidates conclude they do the same job and skip the distinction between a working conductor and a protective conductor.
What to do instead
Learn the one-line rule: neutral completes the circuit and carries load current; earth carries current only under fault and must never be fused or switched. Then answer any question by naming the function first (return path vs. fault path), and link it to why a blown fuse on the neutral is dangerous (equipment stays live).
Calculating power in a circuit by multiplying voltage and current without checking whether the load is resistive or reactive, so a motor load is treated as P = V×I.
Basic DC-style examples dominate early practice, and candidates transfer P = VI directly to AC inductive loads, ignoring power factor and the difference between apparent power (VA) and true power (W).
What to do instead
Adopt a decision step before any power calculation: if the load is a heater or lamp, use P = VI; if it is a motor, fan or transformer, use P = VI×cos φ and label the answer in watts, stating the power factor used. Keep a small table of unit names and symbols (W, VA, var, kWh) and check the unit matches the quantity asked.
Choosing a wiring system (cleat, casing-capping, conduit, batten) for a location without first classifying the location, e.g. specifying ordinary PVC conduit in a damp bathroom or a workshop with mechanical damage risk.
Candidates match wiring systems to building types by memory ('houses use casing-capping') rather than to the actual environmental and mechanical conditions, because the selection criteria are learned as a list without a decision order.
What to do instead
Use a fixed three-question sequence for every wiring-system question: (1) What are the surroundings - dry, damp, corrosive, explosive? (2) What mechanical protection is needed? (3) Is appearance or future rewiring a factor? Then justify the choice in one sentence. Memorise the standard pairings: batten for dry domestic ceilings, casing-capping for surface domestic runs, conduit for damp/industrial, and armoured cable where damage is likely.
Confusing the functions of a fuse, an MCB and an ELCB/RCCB, and answering that an MCB protects a person against electric shock.
All three are grouped as 'protection devices' in revision notes, and their trip mechanisms (overcurrent vs. earth leakage) are not distinguished, so candidates default to 'it protects everything'.
What to do instead
Build a two-column comparison: overcurrent protection (fuse, MCB - protects wiring against overload and short circuit) versus earth-leakage protection (ELCB/RCCB - detects current to earth and protects people, typical 30 mA sensitivity). For each device, state what it senses, what it protects, and one typical rating. Answer exam questions by naming the sensed quantity first.
Describing the shock path or first response to an electric shock incorrectly, such as saying you should pull the victim away by hand or that rubber shoes make it safe to touch a live conductor.
Candidates know 'switch off the supply' as a slogan but have not rehearsed the sequence, so under time pressure they write the intuitive but lethal action of grabbing the person.
What to do instead
Memorise a fixed rescue sequence and write it in order: isolate the supply at the main switch; if isolation is impossible, use a dry insulating object (wooden pole, dry cloth) to separate the victim; do not touch the person with bare hands; call for help; give artificial respiration/CPR if breathing has stopped; get medical aid. Also state the current-path concept (hand-to-hand and hand-to-foot paths cross the heart) to explain why the response matters.
Mixing up step-up and step-down transformer behaviour when tracing power from generation to the consumer, e.g. saying transmission lines operate at low voltage to reduce loss.
The generation–transmission–distribution chain is memorised as a sequence of names without attaching voltage levels and the reason for each transformation, so the direction of voltage change gets reversed.
What to do instead
Draw the chain once with numbers: generation at about 11 kV, step up to high voltage for transmission, step down at substations for distribution, final step down to 230 V single phase / 400 V three phase at the consumer. Attach the reason to each arrow: higher voltage means lower current for the same power, and lower current means lower I²R line loss. Re-draw the diagram from memory before the exam.
Reading an analog multimeter or ammeter without accounting for range selection and scale division, giving answers off by a factor of 10 or reading the wrong scale row.
Candidates learn 'connect in series for current, parallel for voltage' but never practise converting a pointer position on a chosen range into an actual value, which is the step the exam tests.
What to do instead
Practise the conversion aloud: value = (pointer reading / full-scale divisions) × selected range. Before reading, state the range, the full-scale value of the scale used, and the number of divisions. Do five readings on different ranges (e.g. 2.5 V, 10 V, 250 V) and always write the unit after the number.
Using a megger (insulation resistance tester) or a multimeter on the wrong function for the test - e.g. testing insulation continuity with an ordinary ohmmeter, or checking live voltage with the meter set to resistance.
The instruments look similar and the candidate focuses on 'measuring resistance' without linking the required test voltage to the purpose of the test, and without a habit of checking the meter setting before use.
What to do instead
Learn each instrument with three attributes: what it measures, its typical test voltage or range, and its safety rule. For insulation resistance, the answer is a megger at 500 V DC with the supply isolated and the reading expected in megohms; for continuity, a low-reading ohmmeter with supply off. Always write 'supply isolated and proved dead' as the first step of any instrument question.
Writing employability-skills answers as generic personality statements ('I am hardworking and a good team player') instead of demonstrating the behaviour with a concrete workplace example.
These questions feel subjective, so candidates fall back on adjectives learned in school essays, and they have not prepared short structured examples of communication, teamwork or safety reporting.
What to do instead
Prepare four ready-made STAR examples (Situation, Task, Action, Result) - one each for teamwork, communication, problem-solving and following safety procedure - each 3–4 sentences long and drawn from workshop or project work. In the exam, name the skill first, then give the example, then state the result. Replace every adjective with an action verb.