Full Mock #1 — Error Notes
Aamirah Fathima · 30 September 2026 · 180 Q · 720 marks · target 540 · danger line 480 · ILTS on Sunday 4 October
+56
above target · 4 short of 600
1. Section breakdown
Biology alone is 335 / 360. It is ready; the work left is Physics and Chemistry.
2. The three things that cost the paper
- Lenz's law and current direction — 5 questions, 23 marks. Q146, 147 and 152 wrong, Q149 and Q150 blank. Q146 is word-for-word the error she made in the Physics re-test (Q6), and Q147, Q149 and Q150 are cases she answered CORRECTLY in that same re-test. The method is known; it is not yet automatic under time.
- Factor and chaining slips in Physics numericals — 6 questions, 30 marks. Q137 (turns dropped), Q140 (reversal not doubled), Q156 and Q157 (one doubled force carried into the next answer), Q161 (mid-point: half the length means a quarter of the emf), Q163. The re-test scored 7/7 on this block, so this is pressure, not knowledge.
- Six blanks — 24 marks left on the table. Q93, 132, 135 in Chemistry and Q149, 150, 178 in Physics. Chemistry finished 8 below target with 12 marks sitting in its three blanks.
3. What went right
- Every margin correction was right: Q101 → C, Q160 → B, Q166 → B, Q167 → A. Four questions reviewed and all four changed to the correct answer — 20 marks saved by checking.
- Botany 43/45 and Zoology 42/45 across a full-length paper, with zero blanks in 90 Biology questions.
- Chemistry Q106–Q126: 21 in a row correct.
- Three sections finished with no timing collapse; the drop is concentrated in the last section.
Botany — 2 wrong · 0 blank
Q2WrongNAttribution / dateSearch for the genetic material
The year in which the transforming principle was identified as DNA.
Her answer(B) 1958
Correct answer(D) 1944
WhyAvery, MacLeod and McCarty completed the purification by 1944. 1958 is Meselson and Stahl.
Where it went wrong · fixDate card: 1928 Griffith · 1944 Avery · 1952 Hershey–Chase · 1958 Meselson–Stahl.
Q39WrongCStatement judgementDNA replication
How many are correct? A semiconservative · B polymerase works 5′→3′ · C ligase forms a phosphodiester bond · D replication begins anywhere along the molecule.
Her answer(B) Only two
Correct answer(C) Only three
WhyA, B and C are true. Only D is false — replication begins at a definite origin of replication.
Where it went wrong · fixShe rejected one true statement as well as the false one. Mark each statement T or F separately, then count.
Zoology — 3 wrong · 0 blank
Q71WrongSArrangement / orderGene transfer methods
Match: calcium chloride with heat shock · micro-injection · biolistics · vector-mediated transfer.
Her answer(A)
Correct answer(C) A–II, B–IV, C–I, D–III
WhyCaCl₂ + heat shock → transformation of bacterial cells; micro-injection → DNA into the nucleus; biolistics → gold or tungsten particles; disarmed vector → infects the cell.
Where it went wrong · fixRows swapped again. Write all four rows in the margin before reading the options.
Q79WrongCA–R linkPCR
A: The PCR mixture is heated at the start of every cycle. R: Taq polymerase is isolated from a bacterium that lives at high temperature.
Her answer(A) R explains A
Correct answer(B) Both true, R does NOT explain A
WhyBoth statements are true, but the heating is done to denature the DNA. Taq's origin explains why the enzyme survives the heating — not why the heating is done.
Where it went wrong · fixThis is the fine distinction she now needs: R true and relevant to the topic is not the same as R explaining A.
Q82WrongSFigure readingGel electrophoresis
Band P lies closer to the wells than band Q. Therefore…
Her answer(A)
Correct answer(D) P is the larger fragment and Q the smaller
WhyMigration is away from the wells, and smaller fragments travel farther. The band nearer the well is the larger fragment.
Where it went wrong · fixSame figure logic as the re-test, answered correctly there. Mark the direction of migration on the gel before choosing.
Chemistry — 4 wrong · 3 blank
Q91WrongNNCERT recallDetection of extra elements
Fusion with sodium converts the nitrogen of an organic compound into…
Her answer(D) sodium nitrate
Correct answer(C) sodium cyanide
WhySodium fusion gives NaCN, which is why ferrous sulphate then produces Prussian blue.
Where it went wrong · fixChain to memorise: N → NaCN → Prussian blue · S → Na₂S → violet with nitroprusside · halogen → NaX → AgX.
Q93BlankTBlankDetection of extra elements
In the flow chart of tests on the sodium fusion extract, the reagent at Q detects…
Her answerLeft blank
Correct answer(D) sulphur
WhyQ is sodium nitroprusside, which gives the violet colour for sulphide.
Where it went wrong · fixBlank on a chart she has answered before. Label each branch of a flow chart as you read it.
Q96WrongCA–R linkDetection of extra elements
A: The sodium fusion extract must be made alkaline before it is tested. R: Fusion with sodium converts the covalently bound elements into ionic compounds.
Her answer(A) R explains A
Correct answer(B) Both true, R does NOT explain A
WhyBoth are true, but the extract is alkaline because the excess sodium forms NaOH in water — not because fusion ionises the elements.
Where it went wrong · fixSecond A–R link error in this paper (with Q79). R being a true, related fact is not enough.
Q127WrongSFigure readingAnion analysis
Concentrated sulphuric acid added down the side after freshly prepared ferrous sulphate gives the tube shown. The anion is…
Her answer(C)
Correct answer(B) nitrate
WhyThe brown ring at the junction of the two layers is the confirmatory test for nitrate.
Where it went wrong · fixA figure question on a test she knows by name. Say what the figure shows in words before reading the options.
Q132BlankTBlankTitration chemistry
Oxalic acid is titrated against permanganate at 60–70 °C because…
Her answerLeft blank
Correct answer(D) the reaction is slow at room temperature
WhyThe oxalate–permanganate reaction is sluggish when cold, so the mixture is warmed; Mohr's salt needs no warming.
Where it went wrong · fixShe answered this correctly in the Practical Chemistry re-test and left it blank here.
Q134WrongSArrangement / orderTitration chemistry
Match: phenolphthalein · methyl orange · oxalic acid · Mohr's salt.
Her answer(B)
Correct answer(D) A–II, B–IV, C–I, D–III
WhyPhenolphthalein colourless→pink; methyl orange red→yellow; oxalic acid is the primary standard against permanganate; Mohr's salt the standard for the iron(II) titration.
Where it went wrong · fixThe indicator-and-standard match has now been missed twice (Practical Chemistry Q79) and answered correctly once in the re-test. Work the rows first.
Q135BlankTBlankTitration practice
How many are correct? Burette rinsed with its own solution · pipette rinsed · dilute H₂SO₄ used · conical flask rinsed with the titrand.
Her answerLeft blank
Correct answer(C) Only three
WhyThe conical flask is rinsed with distilled water only; rinsing it with the solution would change the quantity titrated.
Where it went wrong · fixThird Chemistry blank in one paper — 12 marks given away in a section that finished 8 below target.
Physics — 11 wrong · 3 blank
Q137WrongSDropped a factorFaraday's law
150 turns, flux change 2 × 10⁻³ Wb in 0.05 s. The emf is…
Her answer(C) 0.04 V
Correct answer(B) 6 V
Whyε = N ΔΦ/Δt = 150 × 2×10⁻³ / 0.05 = 6 V. Her answer is ΔΦ/Δt without the 150 turns.
Where it went wrong · fixWrite N explicitly in every Faraday substitution.
Q140WrongSFactor of 2Faraday's law
100 turns, flux 1.5 × 10⁻³ Wb per turn, REVERSED in 0.06 s. The average emf is…
Her answer(C) 2.5 V
Correct answer(A) 5 V
WhyReversal means ΔΦ = 2 × 1.5×10⁻³ = 3×10⁻³ Wb. ε = 100 × 3×10⁻³ / 0.06 = 5 V. Her answer is exactly half — the factor 2 for reversal was dropped.
Where it went wrong · fixThe word reversed always doubles ΔΦ. Underline it in the question.
Q146WrongCAttract vs repelLenz's law
The south pole of a magnet is WITHDRAWN from a coil. Seen from the magnet, the near face becomes…
Her answer(C) a south pole, with the current clockwise
Correct answer(B) a north pole, with the current anticlockwise
WhyA receding magnet must be attracted, so the near face takes the opposite pole: a receding S pole faces an N face, and an N face means an anticlockwise current from that side.
Where it went wrong · fixIdentical to Q6 of the re-test, which she also got wrong. The four-case table is the single highest-value thing to fix before Sunday.
Q147WrongCDirection reversalLenz's law
A loop moves at constant speed INTO a region where the field is into the page. During the entry…
Her answer(C)
Correct answer(B) the induced current is anticlockwise and the force opposes the motion
WhyInto-page flux is growing, so the induced current makes out-of-page flux inside the loop — anticlockwise — and the force always opposes the motion that causes it.
Where it went wrong · fixShe had this exact case right in the re-test (Q9). Fill the three blanks — flux · growing or dying · sense — before reading the options.
Q149BlankTBlankLenz's law
A copper ring is held coaxially above a solenoid and the switch is closed. The ring…
Her answerLeft blank
Correct answer(C) is pushed upwards
WhySwitching on makes the flux grow, so the ring opposes it and is repelled — pushed upwards.
Where it went wrong · fixLeft blank although she answered the same pair correctly in the re-test (Q12).
Q150BlankTBlankLenz's law
With a steady current flowing, the switch is opened. A ring held below the solenoid is…
Her answerLeft blank
Correct answer(A) pulled towards the solenoid
WhyThe flux is dying, so the induced current flows in the same sense as the solenoid current to maintain it, and parallel currents attract.
Where it went wrong · fixThe partner of Q149 — learn the two as one pair: switch ON → repelled · switch OFF → attracted.
Q152WrongCA–R linkLenz's law
A: A magnet dropped through a vertical copper pipe falls more slowly than in air. R: Copper is not a magnetic material.
Her answer(A) R explains A
Correct answer(B) Both true, R does NOT explain A
WhyBoth are true, but the slowing is caused by eddy currents opposing the motion, not by copper being non-magnetic — if anything, that fact makes the result surprising.
Where it went wrong · fixThird A–R link error in this paper (Q79, Q96, Q152). All three have a Reason that is true and topical but not causal.
Q156WrongSFactor of 2Motional emf
The force needed to keep the rod moving uniformly.
Her answer(C) 1.2 N
Correct answer(D) 0.6 N
WhyF = B²l²v/R. Her answer is exactly twice the correct value.
Where it went wrong · fixFactor-of-2 again, in the chain she had 7/7 on in the re-test.
Q157WrongSCarried errorMotional emf
The power supplied by the external agent in that arrangement.
Her answer(B) 9.6 W
Correct answer(C) 4.8 W
WhyP = Fv, and with the correct F = 0.6 N this gives 4.8 W. She carried her doubled force forward from Q156.
Where it went wrong · fixOne slip became two marks lost. When answers chain, re-check the first before using it.
Q161WrongSMid-point trapRotating rod
Rod 1 m, ω = 5 rad s⁻¹, B = 0.8 T. PD between the axis and the MID-POINT.
Her answer(B) 2 V
Correct answer(D) 0.5 V
Whyε = ½Bω(l/2)² = ½ × 0.8 × 5 × 0.25 = 0.5 V. Her 2 V is ½Bωl² — the value for the full length.
Where it went wrong · fixThe mid-point case: half the length, so a QUARTER of the emf, because the length is squared. This exact trap appeared in both earlier re-tests.
Q163WrongSNumericalTerminal velocity
Rod 50 g on vertical rails, R = 0.4 Ω, B = 0.5 T, l = 0.4 m, g = 10 m s⁻².
Her answer(D)
Correct answer(B) 5 m s⁻¹
WhyAt terminal velocity mg = B²l²v/R, so v = mgR/(B²l²) = 0.05 × 10 × 0.4 / (0.25 × 0.16) = 5 m s⁻¹.
Where it went wrong · fixWrite the balance equation first, then rearrange — do not substitute into a half-remembered formula.
Q169WrongSGraph readingFlux–time graph
The magnitude of the emf in region I of the 50-turn coil graph.
Her answer(D)
Correct answer(B) 30 V
WhyRead the slope off the graph: ΔΦ/Δt over region I, multiplied by N = 50.
Where it went wrong · fixGraph questions: write the two coordinates you are using before calculating the slope.
Q170WrongCConcept gapInduced charge
Two identical coils undergo the same flux change, one quickly and one slowly. The charge that flows is…
Her answer(C) larger in the quicker change
Correct answer(B) the same in both
Whyq = NΔΦ/R — the charge depends only on the total flux change and the resistance, never on how fast it happens. The speed changes the current, not the charge.
Where it went wrong · fixThe one-line rule: emf and current depend on the rate; charge does not.
Q178BlankTBlanka.c. generator
How many of the statements about the a.c. generator are correct?
Her answerLeft blank
Correct answer(C) Only three
WhyThree of the four are standard NCERT; the false one is the statement about slip rings reversing the connections, which is the commutator of a d.c. generator.
Where it went wrong · fixAn easy statement-count question left blank in the last section — a timing casualty.
Repair day — 1 October
- Lenz's law, 90 minutes. Write the four-case table from memory (N approaching → N face, anticlockwise · N receding → S face, clockwise · S approaching → S face, clockwise · S receding → N face, anticlockwise), then redraw and re-solve Q146, 147, 149, 150, 152. Finish with the check: clockwise seen from your side = SOUTH face.
- Physics numericals, 60 minutes. Re-solve Q137, 140, 156, 157, 161, 163, 169 showing every step, and write beside each whether the slip was formula, substitution or arithmetic. Underline the words reversed and mid-point wherever they appear.
- Chemistry, 45 minutes. Q91, 93, 96, 127, 132, 134, 135 — detection of elements, the brown ring, and titration chemistry. All seven are facts she has answered correctly before.
- Biology, 30 minutes only. Q2, 39, 71, 79, 82 — then leave it alone.
- Blanks rule for Mock #2 (2 October, 12:00–3:20 PM): at the 150-minute mark, stop and answer every empty question. Six blanks are worth up to 24 marks; a guess between two options is worth +1.5 on average.
- A–R link: Q79, Q96 and Q152 all had a Reason that was true and on-topic but not causal. Say "A because R" aloud; if it needs a bridge sentence to make sense, the answer is (B).