CBSE · Class 10
Science Formulas for Class 10 (Physics)
Chapter-wise Physics formulas for CBSE Class 10 Science (2026-27) — Light, Electricity and Magnetic Effects chapters with all key formulas, laws and unit tables.
For reference only. Always verify formulas and information against your official NCERT textbooks or board-prescribed materials before use in exams. Learnizo does not guarantee absolute accuracy.
Ch 1.Light — Reflection and Refraction
| Formula / Relation | Expression |
|---|---|
| Mirror formula | 1/f = 1/v + 1/u |
| Magnification (mirror) | m = −v/u = h'/h |
| Focal length vs radius of curvature | f = R/2 |
| Lens formula | 1/f = 1/v − 1/u |
| Magnification (lens) | m = v/u = h'/h |
| Power of lens | P = 1/f (in metres) |
| Combined power (lenses in contact) | P = P₁ + P₂ |
| Snell's Law | n₁ sin θ₁ = n₂ sin θ₂ |
| Refractive index | n = speed of light in vacuum / speed of light in medium = c/v |
| n = sin i / sin r | For medium with respect to air |
Ch 2.Human Eye and Colourful World
| Formula / Relation | Expression |
|---|---|
| Least distance of distinct vision | D = 25 cm (for normal adult eye) |
| Far point of normal eye | ∞ (infinity) |
| Power of corrective lens for myopia | P = −1/far point distance (in metres) |
| Power of corrective lens for hypermetropia | P = +value (convex lens) |
Ch 3.Electricity
| Formula / Relation | Expression |
|---|---|
| Ohm's Law | V = IR |
| Resistance formula | R = ρL/A |
| Resistors in series | R_s = R₁ + R₂ + R₃ + … |
| Resistors in parallel | 1/R_p = 1/R₁ + 1/R₂ + 1/R₃ + … |
| Electric power | P = VI = I²R = V²/R |
| Electrical energy | E = Pt = VIt |
| 1 kWh (unit of electricity) | = 3.6 × 10⁶ J |
| Current definition | I = Q/t |
| Work done by electricity | W = QV = VIt |
| Joule's heating effect | H = I²Rt |
Ch 4.Magnetic Effects of Electric Current
| Formula / Relation | Expression |
|---|---|
| Magnetic field at centre of circular loop | B ∝ I/r |
| Right-hand thumb rule | Thumb → direction of current; fingers curl → direction of magnetic field |
| Fleming's Left-Hand Rule | Force on conductor in magnetic field: Forefinger→B, Middle finger→I, Thumb→Force |
| Fleming's Right-Hand Rule | For induced current in generator: Forefinger→B, Thumb→motion, Middle finger→induced current |
| Force on conductor (F) | F = BIL sin θ |
Frequently Asked Questions
What is the mirror formula and how to use it?
The mirror formula is 1/f = 1/v + 1/u, where f is the focal length, v is the image distance and u is the object distance — all measured from the pole of the mirror using sign convention. For a concave mirror, f is negative (new Cartesian). Object is always placed on the left, so u is negative. Substitute values with signs and solve for the unknown. A positive v means virtual image; negative v means real image.
What is the difference between power and energy in electricity?
Power is the rate of doing work: P = VI = I²R (unit: Watt). Energy is power × time: E = Pt (unit: Joule or kWh). A 100W bulb burning for 10 hours consumes 100 × 10 = 1000 Wh = 1 kWh = 1 unit of electricity. Your electricity bill is based on kWh consumed, not Watts directly.
What is Fleming's Left-Hand Rule used for?
Fleming's Left-Hand Rule determines the direction of force on a current-carrying conductor placed in a magnetic field — it is the principle behind electric motors. Stretch the forefinger (direction of magnetic field B), middle finger (direction of current I), and thumb (direction of force/motion) of the left hand at right angles to each other. The thumb shows the direction the conductor moves.
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