24 hours to exam? This page tells you exactly what to focus on, what to skip, and how to manage your time tomorrow.
CBSE Class 12 Physics
24 Hours Before the Exam
No time for everything. This guide tells you exactly what to revise, which topics almost certainly appear, what mistakes to avoid, and how to manage your 3 hours in the exam hall.
Focus on These Chapters First
- Current Electricity — Kirchhoff's laws, Wheatstone bridge, meter bridge numerical
- Alternating Current — LCR circuit, resonance, power factor, transformer
- Ray Optics — lens maker equation, refraction through prism, microscope/telescope
- Electromagnetic Induction — Faraday's law, Lenz's law, self/mutual inductance
- Electrostatics — Gauss's law, capacitors (series/parallel), energy stored
- Moving Charges — force on conductor, circular motion of charge, cyclotron
- Semiconductor Electronics — p-n junction, forward/reverse bias, logic gates
- Wave Optics — Young's double slit, interference, diffraction
Key Formulas & Facts to Memorise Right Now
- Coulomb's law: F = kq₁q₂/r² | Electric field E = F/q | V = kq/r
- Capacitance: C = Q/V | Energy = ½CV² | Series: 1/C = 1/C₁+1/C₂ | Parallel: C = C₁+C₂
- Ohm's law: V = IR | Resistivity: R = ρL/A | Power: P = I²R = V²/R
- Magnetic force: F = qvB sinθ | F = BIL sinθ | Torque = NIAB sinθ
- Faraday: EMF = -dΦ/dt | Self inductance: EMF = -L(dI/dt)
- Lens formula: 1/f = 1/v - 1/u | Lens maker's: 1/f = (n-1)(1/R₁ - 1/R₂)
- De Broglie: λ = h/mv | Photoelectric: KE_max = hν - φ
- Energy of photon: E = hν = hc/λ | Einstein's mass-energy: E = mc²
Timing Strategy for 3 hours Exam
- 1First 15 min: Read paper — mark questions you can solve in under 3 minutes
- 20–30 min: Section A (MCQs and assertion-reason) — do not spend more than 1 min each
- 330–80 min: Section B (2-mark) and C (3-mark) — show formula → substitution → answer
- 480–150 min: Section D (5-mark) — derivations and numericals, show all steps clearly
- 5150–170 min: Case study — read carefully, relate to known concepts
- 6Last 10 min: Check units, significant figures, and sign in optics answers
Common Mistakes — Avoid These Tomorrow
- ✕Not using consistent sign convention in optics (all distances from pole/optical centre)
- ✕Confusing self-inductance and mutual inductance formulas
- ✕Forgetting to convert units — always work in SI units (metres, kilograms, amperes)
- ✕Not drawing the circuit diagram for current electricity problems
- ✕Writing the wrong formula for peak vs RMS value in AC (Vrms = V₀/√2)
- ✕Leaving derivations incomplete — every step in a derivation carries marks
- ✕Not stating Lenz's law direction before calculating induced EMF
Must Attempt — Never Leave These Blank
- ✓All MCQs — no negative marking, use elimination if unsure
- ✓Any direct formula-substitution numerical — guaranteed marks if formula is right
- ✓Logic gates truth table — always appears, straightforward
- ✓Lens/mirror formula problems — follow steps and you'll get full marks
Skip If Unsure (Return If Time Permits)
- →Complex wave optics derivations if you haven't revised them — attempt later
- →Cyclotron or synchrotron questions if unfamiliar — move on and return
Remember: Partial marks exist. Attempt and leave if stuck — come back if time allows. Never spend more than 8 minutes on a single 5-mark question.
Physics numericals are formula-based. Even if you don't remember derivations, writing the correct formula + units + substitution gets you 3 out of 5 marks. Partial credit adds up.
Night Before — Non-Academic Checklist
Pack your bag
Admit card, 2 pens, pencil, eraser, ruler, geometry box (if needed)
Sleep by 10 PM
Your brain consolidates memory during sleep. Late-night cramming hurts more than it helps
Stop studying at 9 PM
Whatever you don't know by tonight won't be learnt in an hour. Trust your preparation
Set two alarms
One to wake up, one as a backup. Arrive at the centre 30 minutes before the exam
More resources for Class 12 Physics
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