Physics in Class 10 CBSE is one of the most scoring subjects if you focus on understanding formulas and applying them correctly. Unlike theory-heavy subjects, Physics gives you a clear advantage because most questions are numerical or concept-based.
This guide is a complete, deeply structured, and expanded version of the formula sheet explained in the transcript fileciteturn4file0. It not only includes formulas but also explains their meaning, usage, and common mistakes to avoid.
If you revise this sheet consistently, you can confidently attempt almost every numerical question in your board exam.
Chapter 1: Electricity – Complete Formula Sheet
Electricity is one of the highest-weightage chapters in Class 10 Physics. Most students either score full marks here or lose marks due to small calculation mistakes.
Basic Concepts and Formulas
Charge:
Q = I × t
Unit: Coulomb (C)
This formula tells us that charge depends on current and time. It is often used in direct numerical questions.
Current:
I = Q / t
Unit: Ampere (A)
Current represents the flow of electric charge through a conductor.
Potential Difference:
V = W / Q
Unit: Volt (V)
This explains how much work is required to move a unit charge from one point to another.
Ohm’s Law
V = IR
This is one of the most important formulas in electricity. Almost every numerical question in this chapter is based on Ohm’s law.
It shows the relationship between voltage, current, and resistance.
Resistance and Resistivity
Resistance:
R = ρL / A
Unit: Ohm (Ω)
This formula shows that resistance depends on the length and area of the conductor.
Resistivity:
ρ = RA / L
Unit: Ohm-meter (Ωm)
Resistivity is a property of the material and does not depend on size.
Electric Power
P = VI
P = I²R
P = V² / R
Unit: Watt (W)
These three forms of the power formula are extremely important. You should know when to use each one depending on the given data.
Electric Energy
E = P × t
Unit: Joule (J)
Practical unit: kWh (kilowatt-hour)
Electric energy is often asked in application-based questions such as electricity bill calculations.
Heating Effect of Current
H = I²Rt
Unit: Joule (J)
This formula is used in questions related to heating devices like heaters and irons.
Combination of Resistors
Series Combination:
R = R1 + R2 + R3
Parallel Combination:
1/R = 1/R1 + 1/R2 + 1/R3
Important Concept:
- In series → Current remains constant
- In parallel → Voltage remains constant
Memory Trick:
SI → Series → Current same
Understanding this concept clearly helps in solving complex circuit questions easily.
Chapter 2: Light – Reflection and Refraction
This chapter is both conceptual and numerical. Many students lose marks here due to confusion in sign conventions.
Mirror Formula
1/f = 1/v + 1/u
Lens Formula
1/f = 1/v − 1/u
These formulas are used to calculate image distance and focal length.
Magnification
For mirrors:
m = −v/u
For lenses:
m = v/u
Also:
m = height of image / height of object
Nature of Image Based on Magnification
- Positive magnification → Virtual and erect image
- Negative magnification → Real and inverted image
This concept is very important for MCQs and case-based questions.
Refractive Index
n = sin i / sin r
n = v1 / v2
These formulas are used in refraction-related problems and are frequently asked in exams.
Power of Lens
P = 1/f (in meters)
Unit: Diopter (D)
- Positive power → Convex lens
- Negative power → Concave lens
This is one of the most frequently asked formulas in numericals.
Sign Conventions (Very Important)
Sign conventions are extremely important because even a small mistake can lead to a wrong answer.
For Mirrors:
- Object distance (u) is always negative
- Image distance (v) is negative for real images
- Image distance (v) is positive for virtual images
For Lenses:
- Object distance is always negative
- Image distance is positive for real images
- Image distance is negative for virtual images
Tip: Always draw a rough ray diagram before solving numericals.
Chapter 3: Magnetic Effects of Electric Current
This chapter focuses more on concepts, diagrams, and rules rather than formulas.
Magnetic Field Around a Conductor
- Magnetic field increases with current
- Magnetic field decreases with distance
Circular Loop
- Field strength increases with current
- Decreases with radius
Solenoid
- Magnetic field increases with number of turns
- Decreases with distance
Inside solenoid behaves like a bar magnet.
Fleming’s Left-Hand Rule
This rule is used to determine the direction of force acting on a current-carrying conductor in a magnetic field.
This is one of the most important concepts and is frequently asked in exams.
Chapter 4: Human Eye and the Colourful World
This chapter is mostly conceptual but still contains important formulas and diagrams.
Power of Lens
P = 1/f
Defects of Vision
- Myopia → corrected using concave lens
- Hypermetropia → corrected using convex lens
Important Concepts
- Ray diagrams are frequently asked
- Human eye diagram should be practiced regularly
- Understanding image formation is crucial
Important Exam Tips for Physics
- Revise formulas daily to build strong memory
- Practice numericals from NCERT and PYQs
- Always write units in answers
- Focus on sign conventions in Light chapter
- Attempt easy questions first in exam
Common Mistakes to Avoid
- Forgetting units in final answers
- Using incorrect formulas
- Ignoring sign conventions
- Making calculation errors
- Skipping practice of numericals
Avoiding these mistakes can significantly improve your score.
FAQs
Q1. Which chapter is most important in Physics?
Electricity and Light are the most important chapters as they contain the maximum number of numericals. Mastering these chapters can help you score high marks easily.
Q2. How can I memorize formulas effectively?
Instead of rote learning, write formulas daily, revise them regularly, and apply them in numerical problems. This helps in long-term retention and better understanding.
Q3. Are units really important in Physics?
Yes, units are extremely important. Even if your calculation is correct, missing or incorrect units can result in loss of marks.
Q4. How to avoid mistakes in numericals?
Always write the formula first, substitute values carefully, use correct units, and double-check calculations before finalizing the answer.
Q5. How important are sign conventions?
Sign conventions are critical in Light chapter. A small mistake in sign can completely change the answer, so practice them thoroughly.
Q6. Can I revise Physics in one day before exam?
Yes, if you focus on formulas, important concepts, and PYQs. Avoid studying new topics and concentrate only on revision.
Q7. How many numericals should I practice?
You should practice at least 15–20 numericals per chapter to gain confidence and speed.
Q8. Is NCERT enough for Physics?
Yes, NCERT is more than enough if you solve all examples, in-text questions, and exercise questions properly.
Q9. What is the best last-day strategy?
Revise formulas, go through important numericals, and solve previous year questions. Avoid stress and stay confident.
Q10. Which section is easiest to score?
Formula-based numericals are the easiest scoring part if you have practiced well.
Q11. Should I focus more on theory or numericals?
Both are important, but numericals carry more weightage. However, theory helps you understand concepts better.
Q12. How to improve speed in exam?
Practice solving questions with a timer, focus on accuracy, and avoid spending too much time on one question.
Conclusion
Physics becomes one of the easiest subjects if you master formulas and practice regularly. With this complete formula sheet, structured revision, and consistent practice, you can confidently score high marks in your Class 10 CBSE board exams.
Stay consistent, revise daily, and believe in your preparation.
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