Physics in Class 10 CBSE is one of the most scoring subjects when approached strategically. A large portion of the paper, especially numericals and application-based questions, directly depends on formulas. If your formulas are strong and you understand when and how to apply them, you can significantly improve your board exam score.
Many students feel overwhelmed because formulas are spread across multiple chapters. This guide compiles all important formulas in a structured, easy-to-revise format along with explanations, units, applications, and exam tips so that you can revise everything efficiently before your exams.
Chapter-Wise Breakdown of Physics Formulas
Class 10 Physics includes four major chapters:
- Electricity
- Light – Reflection and Refraction
- Magnetic Effects of Electric Current
- Human Eye and the Colourful World
Electricity and Light are highly formula-based chapters, while Magnetic Effects and Human Eye are more conceptual but still require understanding of key relationships and rules.
Electricity Formulas (Highest Weightage Chapter)
Electricity is one of the most important chapters in CBSE Class 10 Physics. Most numericals in exams come from this chapter.
Basic Quantities and Formulas
- Charge: Q = I × t
- Current: I = Q / t
Where:
- Q = Charge (Coulomb)
- I = Current (Ampere)
- t = Time (seconds)
Ohm’s Law
- V = I R
Where:
- V = Potential difference (Volt)
- I = Current (Ampere)
- R = Resistance (Ohm)
This is the most fundamental formula and is frequently used in numericals.
Potential Difference
- V = W / Q
Where:
- W = Work done (Joule)
- Q = Charge (Coulomb)
Electric Power
- P = V I
- P = I² R
- P = V² / R
Unit: Watt (W)
Electrical Energy
- Electrical Energy = P × t
Unit: kilowatt-hour (kWh)
Heating Effect of Current
- H = I² R t
- H = V² t / R
Unit: Joule (J)
Resistance and Resistivity
- R = ρ L / A
- ρ = R A / L
Where:
- ρ = Resistivity
- L = Length
- A = Area of cross-section
Units:
- Resistance: Ohm (Ω)
- Resistivity: Ohm meter (Ω m)
Combination of Resistances
Series Combination:
- R_total = R₁ + R₂ + R₃
Parallel Combination:
- 1/R_total = 1/R₁ + 1/R₂ + 1/R₃
Key Concepts for Exams
- In series → Current remains same
- In parallel → Voltage remains same
- Series increases resistance, parallel decreases resistance
Exam Tip
Always check units carefully in numericals. Many students lose marks due to unit mistakes rather than conceptual errors.
Light – Reflection and Refraction Formulas
This chapter is extremely important for board exams due to numericals and ray diagram-based questions.
Mirror Formula
- 1/f = 1/v + 1/u
Lens Formula
- 1/f = 1/v – 1/u
Magnification
For mirrors:
- m = -v/u
For lenses:
- m = v/u
Also:
- m = h_i / h_o
Where:
- h_i = Height of image
- h_o = Height of object
Sign Convention (Very Important for Numericals)
- Distances measured to the left → Negative
- Distances measured to the right → Positive
- Height above principal axis → Positive
- Height below principal axis → Negative
Important Notes for Exams
- Concave mirror → f is negative
- Convex mirror → f is positive
- Convex lens → f is positive
- Concave lens → f is negative
Image Nature and Position (Quick Understanding)
Concave Mirror
- Real and inverted (most cases)
- Virtual and erect when object is between pole and focus
Convex Mirror
- Always virtual, erect, and diminished
Convex Lens
- Real and inverted (most cases)
- Virtual when object is between focus and optical center
Concave Lens
- Always virtual, erect, and diminished
Common Exam Question Types
- Find image distance using mirror/lens formula
- Calculate magnification
- Identify nature of image
- Draw ray diagrams
Magnetic Effects of Electric Current
This chapter is mostly conceptual but includes important rules and relationships.
Magnetic Field Around a Conductor
- Determined using Right Hand Thumb Rule
Force on Current Carrying Conductor
- Determined using Fleming’s Left Hand Rule
Factors Affecting Magnetic Field
- Current increases → Magnetic field increases
- Distance increases → Magnetic field decreases
Magnetic Field in Circular Loop
- Depends on current and radius
Solenoid
- Inside → Strong and uniform magnetic field
- Outside → Weak and non-uniform field
Key Rules to Remember
- Right Hand Thumb Rule → Direction of magnetic field
- Fleming’s Left Hand Rule → Direction of force
Human Eye and the Colourful World
This chapter has fewer formulas but is important for conceptual clarity.
Power of Lens
- P = 1/f
Where:
- f is in meters
- Unit: Diopter (D)
Key Concepts
- Convex lens → Positive power
- Concave lens → Negative power
Applications
- Used in correcting vision defects like myopia and hypermetropia
Complete Formula Revision Table
| Topic | Formula |
| Charge | Q = It |
| Ohm’s Law | V = IR |
| Power | P = VI |
| Energy | E = Pt |
| Heat | H = I²Rt |
| Mirror | 1/f = 1/v + 1/u |
| Lens | 1/f = 1/v – 1/u |
| Magnification | m = v/u |
| Resistivity | ρ = RA/L |
| Power of Lens | P = 1/f |
Smart Study Tips to Remember Formulas
- Write formulas in your own handwriting
- Stick formula sheet near study desk
- Revise formulas daily for 5–10 minutes
- Practice numericals from NCERT
- Solve previous year questions (PYQs)
- Focus on understanding instead of rote memorization
Common Mistakes to Avoid
- Ignoring sign convention in optics
- Forgetting units in final answer
- Mixing formulas between chapters
- Not revising formulas regularly
- Skipping NCERT examples
High-Scoring Strategy for Physics
- Revise formulas daily
- Practice at least 5 numericals per day
- Focus on Electricity and Light first
- Solve case-based questions
- Revise diagrams and derivations
FAQs
Q1. Which chapter has the most formulas in Class 10 Physics?
Electricity and Light chapters contain the highest number of formulas and are most important for scoring.
Q2. How can I remember all physics formulas easily?
Write them daily, revise regularly, and practice numericals to strengthen memory.
Q3. Is sign convention important in exams?
Yes, incorrect sign usage can lead to wrong answers even if your calculation is correct.
Q4. Which formulas are most important for CBSE boards?
Ohm’s Law, Power formulas, Mirror formula, and Lens formula are extremely important.
Q5. How often should I revise formulas before exams?
Daily revision is recommended, especially in the last 1–2 months before exams.
Conclusion
Mastering physics formulas is the foundation of scoring high marks in Class 10 CBSE exams. Instead of memorizing blindly, focus on understanding how each formula is derived and applied.
With consistent revision, smart practice, and proper strategy, you can confidently solve numericals and boost your overall Physics score.
Make formula revision a daily habit, and Physics will become one of your strongest subjects in CBSE Boards 2026.
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