META DESCRIPTIONWBCHSE Class XII Semester III Model Question Bank Part 23 with advanced Physics, Chemistry, Biological Science, Mathematics, English and Bengali practice, case studies, assertion-reason questions, numericals, HOTS, writing tasks, mock assessment and score improvement strategies.KEYWORDSWBCHSE Class 12 Semester 3WBCHSE Class XII Question BankWBCHSE Model QuestionsWBCHSE Semester III PracticeClass 12 Physics PracticeClass 12 Chemistry PracticeClass 12 Biological ScienceClass 12 Mathematics PracticeClass 12 English PracticeClass 12 Bengali PracticeWBCHSE HOTS QuestionsWBCHSE Case Study QuestionsAssertion Reason QuestionsNumerical PracticeCompetency Based QuestionsHigher Secondary PreparationClass 12 Mock TestWBCHSE RevisionExam StrategyScore ImprovementStudent Study PlanClass 12 Exam PreparationHASHTAGS#WBCHSE#Class12#Semester3#WBCHSEQuestionBank#ModelQuestions#Physics#Chemistry#BiologicalScience#Mathematics#English#Bengali#HOTS#CaseStudy#AssertionReason#Numericals#MockTest#Revision#ExamPreparation#HigherSecondary#StudyStrategy#ScoreImprovement#StudentSuccess#PracticeTest#Class12PreparationEND OF PART 23Next Part: Part 24 — Ultimate Competency Challenge • Full Subject-Wise Mock Papers • Multi-Step Numericals • Data-Based Biology • Advanced Calculus & Probability • English/Bengali Long-Answer Mastery • Complete Mistake-to-Marks Conversion System.Complete the missing answer keysAdd marks, timing, and instructionsAlign question numbering across subjects

September 15, 2026

WBCHSE Class XII Semester III — Subject-Wise Model Question Bank — Part 23

WBCHSE CLASS XII SEMESTER III

Subject-Wise Model Question Bank — Part 23

GRAND MIXED PRACTICE • FULL-LENGTH SUBJECT TESTS • ADVANCED CASE STUDIES • ASSERTION–REASON MARATHON • NUMERICAL MARATHON • WRITING SKILLS • SCORE IMPROVEMENT SYSTEM

INTRODUCTION

Welcome to Part 23 of the WBCHSE Class XII Semester III Subject-Wise Model Question Bank.

At this stage of preparation, students should gradually move beyond simple chapter-wise practice.

The examination may not always ask:

“State the formula.”

Instead, it may ask:

“What happens if the condition changes?”

It may not directly ask:

“Define mutation.”

It may present a situation and ask:

“What biological consequence can follow from this change?”

It may not simply ask for differentiation.

It may combine differentiation with interpretation.

Therefore, Part 23 focuses on mixed-concept thinking.

The target is:

Knowledge → Understanding → Application → Analysis → Accuracy

Remember:

A strong student does not merely know the answer. A strong student knows why the answer is correct.

PART I — PHYSICS

SECTION A — GRAND CONCEPT TEST

Question 1

A capacitor is connected to a battery and fully charged. The battery is then disconnected.

If the plate separation is increased, which quantity definitely remains unchanged?

A. Potential difference

B. Capacitance

C. Charge

D. Stored energy

Question 2

Two resistors (R) and (2R) are connected in parallel.

The equivalent resistance is:

A. (3R)

B. (2R)

C. (\frac{2R}{3})

D. (\frac{R}{3})

Question 3

A charged particle enters a magnetic field with velocity parallel to the field.

The magnetic force is:

A. Maximum

B. Zero

C. Infinite

D. Variable but never zero

Question 4

The direction of induced current is determined by:

A. Ohm's law

B. Coulomb's law

C. Lenz's law

D. Kirchhoff's law

Question 5

If the potential difference across a resistor is doubled while resistance remains constant, electrical power becomes:

A. Half

B. Double

C. Four times

D. Eight times

SECTION B — ASSERTION–REASON MARATHON

Choose:

A. Both Assertion and Reason are true, and Reason correctly explains Assertion.

B. Both are true, but Reason does not correctly explain Assertion.

C. Assertion is true but Reason is false.

D. Assertion is false but Reason is true.

Question 6

Assertion: The electric field inside an ideal conductor in electrostatic equilibrium is zero.

Reason: Free charges redistribute themselves so that electrostatic equilibrium is established.

Question 7

Assertion: Increasing resistance at constant voltage decreases current.

Reason: According to Ohm's law,

[ I=\frac VR ]

Question 8

Assertion: Magnetic force can change the direction of velocity of a charged particle without necessarily changing its speed.

Reason: Magnetic force is perpendicular to the instantaneous velocity.

Question 9

Assertion: Induced emf can be produced without a battery.

Reason: A changing magnetic flux can induce emf.

SECTION C — CASE STUDY

A student connects a resistor to a variable voltage source and records:

(V)

(I)

2 V

0.5 A

4 V

1.0 A

6 V

1.5 A

8 V

2.0 A

Question 10

Determine whether the resistor approximately obeys Ohm's law.

Question 11

Calculate its resistance.

Question 12

What would be the current at 10 V if the same behaviour continues?

Question 13

What would the (V-I) graph look like?

Question 14

What physical condition must remain approximately constant for Ohm's law to hold?

SECTION D — NUMERICAL MARATHON

Question 15

Two capacitors of (3,\mu F) and (6,\mu F) are connected in parallel across a 12 V source.

Find:

equivalent capacitance,

total charge,

energy stored.

Question 16

A resistor of (10\Omega) carries a current of 2 A.

Calculate:

potential difference,

power dissipated.

Question 17

A charge of (2\times10^{-6}C) moves through a potential difference of 50 V.

Calculate the change in electrical potential energy.

SECTION E — MAGNETISM HOTS

Question 18

Why does a charged particle moving perpendicular to a uniform magnetic field follow a circular path?

Explain using the direction of magnetic force.

Question 19

A charged particle enters a magnetic field at an angle other than (0^\circ) or (90^\circ).

What type of path can result?

Explain conceptually.

SECTION F — EMI CHALLENGE

Question 20

Two identical coils experience the same change in magnetic flux.

In one case the change occurs in 1 second and in another case in 0.1 second.

Which case produces greater induced emf?

Explain.

PHYSICS ANSWER KEY

Question 10

Yes, approximately.

The ratio (V/I) remains constant.

Question 11

[ R=\frac{2}{0.5}=4\Omega ]

Question 12

[ I=\frac{10}{4}=2.5A ]

Question 15

Parallel combination:

[ C_{eq}=3+6=9\mu F ]

Total charge:

[ Q=CV ]

[ Q=9\times10^{-6}\times12 ]

[ Q=108\mu C ]

Energy:

[ U=\frac12CV^2 ]

[ U=\frac12(9\times10^{-6})(144) ]

[ U=6.48\times10^{-4}J ]

Question 16

[ V=IR=2\times10=20V ]

[ P=VI=20\times2=40W ]

Question 20

The 0.1-second case produces greater emf because the rate of change of magnetic flux is greater.

PART II — CHEMISTRY

SECTION A — ELECTROCHEMISTRY

Question 21

In a galvanic cell, oxidation occurs at:

A. Cathode

B. Anode

C. Salt bridge

D. External wire

Question 22

Which statement about the salt bridge is correct?

A. It prevents ion movement

B. It maintains electrical neutrality

C. It produces the electrodes

D. It stops the redox reaction

Question 23

If the resistance of an electrolyte solution increases, its conductance:

A. Increases

B. Decreases

C. Remains infinite

D. Becomes zero in every case

SECTION B — NERNST THINKING

Question 24

Why is the cell potential not necessarily constant when concentrations of reactants and products change?

Question 25

Explain qualitatively what happens to cell potential when the reaction quotient changes.

SECTION C — KINETICS

Question 26

For a first-order reaction:

[ k=0.231,min^{-1} ]

Calculate the half-life.

Question 27

A reaction has a half-life of 20 minutes.

What is the approximate fraction of reactant remaining after:

20 min?

40 min?

60 min?

Question 28

How does temperature generally influence reaction rate?

Explain in terms of molecular collisions and activation energy.

SECTION D — COORDINATION CHEMISTRY

Question 29

For:

[ [Co(NH_3)_5Cl]Cl_2 ]

identify:

coordination entity,

central metal,

ligand types,

coordination number,

oxidation state of cobalt.

Question 30

What is the difference between a ligand and a counter ion?

SECTION E — ASSERTION–REASON

Question 31

Assertion: A first-order reaction has a constant half-life at constant temperature.

Reason: The half-life of a first-order reaction is independent of its initial concentration.

Question 32

Assertion: Increasing temperature can increase reaction rate.

Reason: A larger fraction of molecules can possess energy equal to or greater than activation energy.

Question 33

Assertion: A catalyst changes the equilibrium constant.

Reason: A catalyst provides an alternative pathway with lower activation energy.

CHEMISTRY ANSWER KEY

Question 26

[ t_{1/2}=\frac{0.693}{0.231}=3,min ]

Question 27

After 20 min:

[ \frac12 ]

After 40 min:

[ \frac14 ]

After 60 min:

[ \frac18 ]

Question 29

Coordination entity:

[ [Co(NH_3)_5Cl]^{2+} ]

Central metal: Co

Ligands:

(NH_3)

(Cl^-)

Coordination number = 6

Oxidation state:

[ x+0(5)-1=+2 ]

[ x=+3 ]

Therefore cobalt is in the (+3) oxidation state.

PART III — BIOLOGICAL SCIENCE

SECTION A — MOLECULAR BIOLOGY

Question 34

Why is DNA replication called semi-conservative?

Question 35

Differentiate between:

transcription and translation.

Question 36

Why are codons important in protein synthesis?

Question 37

What is the role of tRNA during translation?

SECTION B — CASE STUDY

A DNA segment undergoes a base substitution.

Question 38

What is a point mutation?

Question 39

Can a base substitution have no effect on the protein?

Explain.

Question 40

Can a mutation alter the phenotype?

Explain.

SECTION C — EVOLUTION

Question 41

Why is genetic variation important for natural selection?

Question 42

Explain how environmental conditions can influence which variations become advantageous.

Question 43

Why should fossils be considered evidence for evolutionary history?

SECTION D — STATEMENT ANALYSIS

Question 44

Evaluate:

“An organism develops a useful characteristic because it needs it.”

Give a scientifically reasoned explanation.

Question 45

Evaluate:

“All mutations are harmful.”

SECTION E — DIAGRAM MARATHON

Practise drawing, without looking at the textbook:

DNA replication fork

transcription process

translation process

basic structure of a chromosome

After drawing, check:

☐ Labels

☐ Direction

☐ Sequence

☐ Spelling

☐ Arrows

BIOLOGY ANSWER KEY

Question 34

DNA replication is semi-conservative because each daughter DNA molecule contains one parental strand and one newly synthesised strand.

Question 35

Transcription: DNA information is copied into RNA.

Translation: Information in mRNA is used to synthesise a protein.

Question 39

Yes. A substitution may be a silent mutation if the altered codon still specifies the same amino acid.

Question 41

Variation provides differences among individuals. Natural selection can favour variations that increase survival or reproductive success.

Question 45

False.

Mutations can be harmful, neutral or beneficial depending on their nature and environmental context.

PART IV — MATHEMATICS

SECTION A — CALCULUS MARATHON

Question 46

Differentiate:

[ y=x^3e^x ]

Question 47

Differentiate:

[ y=\frac{\sin x}{x} ]

Question 48

Evaluate:

[ \int(4x^3-6x+5),dx ]

Question 49

Find the stationary points of:

[ f(x)=x^3-3x^2+2 ]

SECTION B — DIFFERENTIAL EQUATION

Question 50

Solve:

[ \frac{dy}{dx}=2x+4 ]

Question 51

What is meant by the order of a differential equation?

SECTION C — VECTORS

Let:

[ \vec a=\hat i+2\hat j+2\hat k ]

[ \vec b=2\hat i-\hat j+\hat k ]

Question 52

Find:

[ \vec a\cdot\vec b ]

Question 53

Find:

[ |\vec a| ]

Question 54

Determine whether the vectors are perpendicular.

SECTION D — PROBABILITY

Question 55

Two coins are tossed.

Find the probability of getting:

two heads,

exactly one head,

at least one head.

Question 56

A die is thrown once.

Find the probability of obtaining a prime number.

SECTION E — 3D GEOMETRY

Question 57

What are direction cosines?

Question 58

If a line has direction ratios (2,3,6), find the corresponding direction cosines.

SECTION F — ERROR HUNT

A student writes:

[ \frac{d}{dx}(x^2\sin x)=2x\sin x ]

Identify the missing term.

MATHEMATICS ANSWER KEY

Question 46

Using product rule:

[ \frac{dy}{dx}

3x^2e^x+x^3e^x ]

[ =e^x(3x^2+x^3) ]

Question 47

Using quotient rule:

[ \frac{dy}{dx}

\frac{x\cos x-\sin x}{x^2} ]

Question 48

[ x^4-3x^2+5x+C ]

Question 49

[ f'(x)=3x^2-6x ]

[ 3x(x-2)=0 ]

Thus:

[ x=0,;2 ]

At (x=0):

[ f(0)=2 ]

At (x=2):

[ f(2)=8-12+2=-2 ]

Stationary points:

[ (0,2),;(2,-2) ]

Question 50

[ y=x^2+4x+C ]

Question 52

[ \vec a\cdot\vec b

1(2)+2(-1)+2(1) ]

[ =2-2+2=2 ]

Therefore the vectors are not perpendicular.

Question 53

[ |\vec a|

\sqrt{1^2+2^2+2^2} ]

[ =\sqrt9=3 ]

Question 55

Sample space:

[ HH,HT,TH,TT ]

Two heads:

[ \frac14 ]

Exactly one head:

[ \frac24=\frac12 ]

At least one head:

[ \frac34 ]

Question 56

Prime numbers on a die:

[ 2,3,5 ]

Therefore:

[ P=\frac36=\frac12 ]

PART V — ENGLISH

SECTION A — UNSEEN PASSAGE

Read the passage:

A good examination strategy is not simply a strategy for answering questions. It is also a strategy for managing attention. When students spend too much time on one difficult question, they may lose the opportunity to answer several easier questions later. A balanced approach is therefore important. Students should identify questions they can answer confidently, complete them carefully, and then return to questions requiring greater thought.

Questions

What is the main message of the passage?

Why can spending too much time on one question be harmful?

What strategy does the writer recommend?

Find a word meaning “carefully considered”.

Give a suitable title.

SECTION B — SUMMARY WRITING

Question 59

Write a summary of the passage in approximately one-third of its original length.

Give an appropriate title.

SECTION C — ARTICLE WRITING

Question 60

Write an article on:

“How Technology Can Improve Student Learning”

Discuss:

online resources,

digital notes,

educational videos,

practice platforms,

dangers of distraction,

balanced use.

SECTION D — REPORT WRITING

Question 61

Write a report on:

“A Career Counselling Programme Organised by Your Institution”

Include:

date,

venue,

speaker/counsellor,

subjects discussed,

student participation,

conclusion.

SECTION E — FORMAL LETTER

Question 62

Write a letter to the appropriate authority requesting improved library facilities for senior students.

Mention:

insufficient books,

reference materials,

study environment,

proposed improvements.

SECTION F — GRAMMAR MASTER TEST

Question 63

Change into passive voice:

“The committee organised the programme.”

Question 64

Change into indirect speech:

The teacher said, “You should revise the chapter.”

Question 65

Correct:

“He has been studying since two hours.”

Question 66

Combine:

He worked hard. He did not succeed.

Use an appropriate conjunction.

SECTION G — LITERATURE ANSWER FRAME

For a long-answer question, use:

Paragraph 1 — Direct answer

State your central point.

Paragraph 2 — Evidence

Refer to the relevant incident, image, character or idea.

Paragraph 3 — Interpretation

Explain what it reveals.

Paragraph 4 — Conclusion

Connect the evidence back to the question.

Avoid memorising unnecessarily long answers.

Understand first. Write second.

ENGLISH ANSWER KEY

Question 63

The programme was organised by the committee.

Question 64

The teacher advised the students that they should revise the chapter.

Question 65

Correct:

He has been studying for two hours.

Question 66

He worked hard, but he did not succeed.

PART VI — BENGALI

বাংলা — গ্র্যান্ড প্র্যাকটিস

A. গদ্য

প্রশ্ন ৬৭

গদ্যের কোনও চরিত্রের মূল্যায়ন করতে গেলে নিম্নলিখিত বিষয়গুলি কীভাবে ব্যবহার করবে?

চরিত্রের কাজ

কথাবার্তা

অন্য চরিত্রের সঙ্গে সম্পর্ক

মানসিক পরিবর্তন

লেখকের দৃষ্টিভঙ্গি

প্রশ্ন ৬৮

“লেখকের ভাষাশৈলী একটি রচনার বক্তব্যকে প্রভাবিত করে।”

উক্তিটি বিশ্লেষণ করো।

B. পদ্য

প্রশ্ন ৬৯

কবিতায় প্রকৃতির চিত্র কীভাবে মানুষের অনুভূতি প্রকাশের মাধ্যম হতে পারে?

প্রশ্ন ৭০

কবিতার অলংকার কীভাবে ভাবপ্রকাশকে শক্তিশালী করে?

C. উদ্ধৃতিভিত্তিক উত্তর

প্রশ্ন ৭১

কোনও উদ্ধৃতির ব্যাখ্যা করতে গেলে কেন শুধু আক্ষরিক অর্থ লিখলে পূর্ণাঙ্গ উত্তর হয় না?

D. ব্যাকরণ

প্রশ্ন ৭২

সমাস নির্ণয় করো:

নীলকমল

প্রশ্ন ৭৩

সন্ধি বিচ্ছেদ করো:

হিমালয়

প্রশ্ন ৭৪

বাক্যটির প্রকৃতি নির্ণয় করো:

“যে ছাত্র নিয়মিত পড়াশোনা করে, সে পরীক্ষায় ভালো ফল করে।”

E. প্রবন্ধ

প্রশ্ন ৭৫

প্রবন্ধ লেখো:

“পরিশ্রম ও সাফল্য”

আলোচনার বিষয়:

পরিশ্রমের অর্থ

প্রতিভা ও পরিশ্রম

ব্যর্থতা থেকে শিক্ষা

নিয়মিত অনুশীলন

আত্মবিশ্বাস

উপসংহার

F. বিশ্লেষণধর্মী রচনা

প্রশ্ন ৭৬

“পরীক্ষায় ভালো ফলের পাশাপাশি প্রকৃত শিক্ষা অর্জনও গুরুত্বপূর্ণ।”

বিষয়টি বিশ্লেষণ করো।

বাংলা উত্তর লেখার সূত্র

একটি বিশ্লেষণধর্মী উত্তরের জন্য:

মূল বক্তব্য → প্রসঙ্গ → ব্যাখ্যা → উদাহরণ/উদ্ধৃতি → বিশ্লেষণ → উপসংহার

এই কাঠামো ব্যবহার করলে উত্তর সাধারণ বর্ণনা থেকে বিশ্লেষণধর্মী উত্তরে উন্নীত হয়।

PART VII — GRAND SIX-SUBJECT RAPID TEST

এবার প্রতিটি বিষয় থেকে একটি করে challenge question।

Physics

Question 77

Why does Lenz's law oppose the change in magnetic flux rather than simply oppose the magnetic field?

Chemistry

Question 78

Why does a catalyst not change the final equilibrium composition when temperature remains constant?

Biology

Question 79

Explain why a mutation can be inherited only under appropriate biological circumstances.

Mathematics

Question 80

Find:

[ \frac{d}{dx}(x^2e^x) ]

English

Question 81

Write 100–120 words on:

“The Value of Learning from Failure.”

Bengali

প্রশ্ন ৮২

“ব্যর্থতা মানুষকে থামিয়ে দিতে পারে, আবার সঠিকভাবে গ্রহণ করলে এগিয়েও দিতে পারে।”

বক্তব্যটির তাৎপর্য ব্যাখ্যা করো।

PART VIII — 30-MINUTE SPEED CHALLENGE

Set a timer for 30 minutes.

Do not use books.

Attempt:

5 Physics questions

5 Chemistry questions

5 Biology questions

5 Mathematics questions

1 English writing task

1 Bengali analytical question

Then stop.

Do not continue beyond the planned time.

The purpose is not only knowledge.

It is:

SPEED + ACCURACY + DECISION MAKING

PART IX — SCORE ANALYSIS SHEET

After every test, record:

Search This Blog

STAR TRUE BRILLIANT

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