#hsc 12th
- Derive an expression for electric potential due to a point charge. Answer: V = 1/4πε₀q/r Let a point charge +q be at O. We find the potential at P, at distance r from O. Potential at P is the work done in br... 1
- Obtain an expression for the de-Broglie wavelength associated with an electron accelerated from rest through a potential difference of ‘V’ volts. Answer: λ = h/√(2meV) ≈ 1.23/√(V) nm An electron (mass m , charge e ) accelerated from rest through a p.d. V gains kinetic energy 1/2mv² = e... 1
- With a neat circuit diagram, explain the working of a full wave rectifier. Draw input–output waveforms. Answer: A full wave rectifier (bridge type) uses four diodes so that current flows through the load in the same direction during both half c... 1
- The string of a guitar is 80 cm long and has a fundamental frequency of 112 Hz. If a guitarist wishes to produce a frequency of 160 Hz, where should he press the string? Answer: He should press the string so that the vibrating length is 56 cm, i.e. 24 cm from one end (56 cm from the other end). For a stretche... 1
- 0.5 mole of an ideal gas at 300 K, expands isothermally from an initial volume of 2 L to a final volume of 6 L. Calculate : (a) work done by the gas (b) heat supplied to the gas [ Given : R = 8.31 J mol\(^{-1}\) K\(^{-1}\) ] Answer: (a) W ≈ 1369 J (about 1.37 kJ) (b) Q = W ≈ 1369 J (a) For an isothermal process, W = nRTlnV_f/V_i = 2.303 nRTlog₁₀V_f/V_i W = 2.303... 1
- A galvanometer has a resistance of 40 \(\Omega\) and a current of 4 mA is needed for full scale deflection. What is the resistance and how is it to be connected to convert the galvanometer (a) into an ammeter of 0.4 A range and (b) into a voltmeter o… Answer: (a) A shunt of about 0.404 Ω in parallel with the galvanometer. (b) A resistance of 1210 Ω in series with the galvanometer. G = 40\... 1
- When a number of droplets coalesce to form a single drop, the total surface area of the drop _____. Answer: A. decreases Answer: (a) decreases When n droplets of radius r join, volume is conserved: 4/3π R³ = n·4/3π r³ , so R = n^(1/3) r . T... 1
- In an ideal gas, molecules possess _____. Answer: A. only kinetic energy Answer: (a) only kinetic energy In an ideal gas there are no intermolecular forces (except during collisions)... 1
- If the frequency of incident radiation is increased above threshold frequency, keeping intensity and potential constant then the photoelectric current _____. Answer: C. remains same Answer: (c) remains same The photoelectric current depends on the number of photoelectrons emitted per second, which... 1
- The process in which heat is neither absorbed nor released by a system is called _____. Answer: D. adiabatic Answer: (d) adiabatic In an adiabatic process Q = 0 : no heat enters or leaves the system. Isobaric means constant pres... 1
- The period of conical pendulum in terms of its length \((l)\), semi-vertical angle \((\theta)\) and acceleration due to gravity \((g)\) is _____. Answer: C. 4π√(lcosθ/4g) Answer: (c) 4π√(lcosθ/4g) For a conical pendulum, Tcosθ = mg and Tsinθ = mω² r with r = lsinθ . Dividing, ω² = g/lc... 1
- A conducting rod of length \(l\), rotates about one of its ends in a uniform magnetic field \(B\), with a constant angular velocity \(\omega\). If the plane of rotation is perpendicular to \(B\), the e.m.f. induced between the ends of rod is _____. Answer: A. 1/2Bω l² Answer: (a) 1/2Bω l² In one rotation (time T = 2π/ω ) the rod sweeps an area π l² , so the flux cut is Bπ l² . Hence e =... 1
- A metal surface is illuminated by photons of energy 5 eV and 2.5 eV respectively. The ratio of their wavelengths of emitted radiation is _____. Answer: B. 1 : 2 Answer: (b) 1 : 2 For a photon E = hc/λ , so λ ∝ 1/E . λ₁/λ₂ = E₂/E₁ = 2.5/5 = 1/2 The ratio of the wavelengths of the two... 1
- A particle is subjected to two parallel S.H.M.s such that \(x = 2\sin\omega t\) and \(y = 2\sin\left(\omega t + \dfrac{\pi}{3}\right)\). The amplitude of the resultant S.H.M. will be _____. Answer: B. 2√(3) Answer: (b) 2√(3) For two parallel S.H.M.s of the same period, A_R = √(A₁² + A₂² + 2A₁A₂cosδ) . Here A₁ = A₂ = 2 , δ = π/3... 1
- A bar magnet of magnetic moment 10 A m\(^2\) has a cross-sectional area of \(2.5 \times 10^{-4}\) m\(^2\). If the intensity of magnetisation of magnet is \(10^6\) A/m, the length of the bar magnet is _____. Answer: B. 4 cm Answer: (b) 4 cm Intensity of magnetisation M_z = m/V = m/A l , so l = m/M_z A = frac1010⁶ × 2.5×10⁻⁴ = 10/250 = 0.04\ m = 4... 1
- In series LCR circuit for \(X_L > X_C\), \(\tan\phi\) will be _____. Answer: C. positive Answer: (c) positive For a series LCR circuit tanφ = X_L - X_C/R . When X_L > X_C the numerator is positive, so tanφ is... 1
- State the formula for electric field intensity due to uniformly charged spherical shell. Answer: Outside the shell E = 1/4πε₀q/r² ; on the surface E = σ/ε₀ ; inside E = 0 . For a shell of radius R carrying charge q (surface charg... 1
- Complete the activities as per the instructions given below : (16 marks)Q.4 (A) Attempt ‘Any One’ of the following activities : (4 marks)(I) Drafting a virtual message : Mr. Avinash has been invited to attend a birthday programme. His son Rohit is at… Answer: A short, clear message giving the reason, the time and instructions — about 50 words. Message Date : 10th February, 2026 Time : 4.00... 1
- Read the extract and complete the activities given below : (10 marks)Home again, I see him drinking weak tea,Eating a stale chapati, reading a book.He goes into the toilet to contemplateMan’s estrangement from a man-made world.Coming out he trembles… Answer: A1 — (c) and (d); A4 — Alliteration (with a touch of paradox/irony). Full answers below. A1. (c) Isolation from the society makes th... 1
- Complete the activities as per the instructions given below : (16 marks)Q.4 (A) Attempt ‘Any One’ of the following activities : (4 marks)(II) Statement of purpose : Imagine, after your HSC Exam, you wish to pursue a ‘Bachelor’s degree in Performing A… Answer: An SOP covering background, passion, achievements, why this course and university, and career goal (about 150 words). Statement of P... 1
- Appreciation : (4 marks)Read the extract and write the appreciation of the poem :Weavers, weaving at break of day,Why do you weave a garment so gay ? ......Blue as the wing of a halcyon wild,We weave the robes of a new-born child.Weavers, weaving at… Answer: Appreciation of ‘Indian Weavers’ by Sarojini Naidu (rhyme scheme aabb; similes, apostrophe, interrogation, repetition, alliteration,... 1
- Complete the activities as per the instructions given below : (16 marks)Q.4 (A) Attempt ‘Any One’ of the following activities : (4 marks)(III) Group Discussion : Imagine, your class has attended a guest lecture on ‘positive thinking.’ Write a group d… Answer: A dialogue among four students that opens the topic, gives points for and examples, adds a balancing view and ends with a conclusion... 1
- Complete the activities as per the instructions given below : (16 marks)Q.4 (B) Attempt ‘Any One’ from the given activities : (4 marks)(I) E-mail : Draft an ‘E-mail’ to a director of a company, requesting him/her to help, support and facilitate educa… Answer: A formal e-mail with To, Subject, salutation, request, list of needs, benefits and closing (about 150 words). From : principal.shivn... 1
- Complete the activities as per the instructions given below : (16 marks)Q.4 (B) Attempt ‘Any One’ from the given activities : (4 marks)(II) Report Writing : Imagine, your class attended a lecture on ‘Self defense and Safety,’ delivered by an expert s… Answer: A report with headline, place and date line, the event in order (who, what, when, where, why), and the outcome (about 150 words). St... 1