Most Scoring Numerical Problems On Capacitance For Boards

Most Scoring Numerical Problems on Capacitance for Boards

Capacitance is one of the most scoring chapters in Physics—especially in board exams. Most questions are formula-based, predictable, and easy to solve if your concepts are clear.

In this guide, we’ll cover important formulas, step-by-step numerical solving methods, common mistakes, and exam strategies.

What is Capacitance? (Quick Revision)

Capacitance is the ability of a conductor to store charge.

Formula: C = Q / V

• C = Capacitance
• Q = Charge
• V = Potential difference

Key Formulas You Must Remember

Real-Life Analogy (Understand Easily)

Key Idea: Bigger tank → more water stored → higher capacitance

Most Scoring Numerical Type 1: Basic Capacitance

Question: A capacitor stores 6 μC charge at a potential of 3V. Find capacitance.

Solution:

C = Q / V = (6 × 10⁻⁶) / 3 = 2 × 10⁻⁶ F

Final Answer: 2 μF

Most Scoring Numerical Type 2: Parallel Plate Capacitor

Question: Find capacitance if area = 2 m² and distance = 0.01 m.

Solution:

C = ε₀ A / d

C = 8.85 × 10⁻¹² × (2 / 0.01)

C = 1.77 × 10⁻⁹ F

Final Answer: 1.77 nF

Most Scoring Numerical Type 3: With Dielectric

Question: A dielectric of constant 5 is inserted. Find new capacitance if original is 2 μF.

Solution:

C' = K × C = 5 × 2 = 10 μF

Final Answer: 10 μF

Concept Check Table (Important for Boards)

Most Scoring Numerical Type 4: Series Combination

Question: Two capacitors 4μF and 6μF are in series. Find equivalent capacitance.

Solution:

1/C = 1/4 + 1/6

1/C = (3 + 2) / 12 = 5/12

C = 12/5 = 2.4 μF

Final Answer: 2.4 μF

Most Scoring Numerical Type 5: Parallel Combination

Question: Capacitors 3μF and 5μF are in parallel. Find total capacitance.

Solution:

C = 3 + 5 = 8 μF

Final Answer: 8 μF

Series vs Parallel Comparison

Most Scoring Numerical Type 6: Energy Stored

Question: Find energy stored in a capacitor where C = 2μF and V = 10V.

Solution:

U = 1/2 CV²

U = 1/2 × 2 × 10⁻⁶ × 100

U = 1 × 10⁻⁴ J

Final Answer: 0.0001 J

Important Exam Trick

If voltage doubles, energy becomes 4 times because energy is proportional to V².

Most Scoring Numerical Type 7: Charge Sharing

Shortcut:

• Total charge remains constant
• Final voltage becomes same

Common Mistakes Students Make

Problem: Students confuse series and parallel formulas.

Agitate: This leads to wrong answers and loss of marks in exams.

Solution: Series = Smaller capacitance Parallel = Larger capacitance

Common Mistakes vs Correct Approach

Case Study (Exam-Level Question)

Question: A 4μF capacitor is connected to a 12V battery. Battery is removed and dielectric (K=2) is inserted. Find new energy.

Solution:

Initial Energy:

U = 1/2 × 4 × 10⁻⁶ × 144 = 2.88 × 10⁻⁴ J

After dielectric (battery removed):

U' = U / K = (2.88 × 10⁻⁴) / 2 = 1.44 × 10⁻⁴ J

Final Answer: 1.44 × 10⁻⁴ J

Strategy to Score Full Marks

Practice Tip

Don’t just read—solve at least 20 numericals to improve speed and accuracy.

Download Free Notes & Practice Questions

When to Use Which Formula

Need Help?

If you still have doubts, get guidance from our experts.

Fill Inquiry Form for Free Guidance

Final Motivation

Capacitance is one of the highest scoring topics in Physics. With clear concepts, regular practice, and avoiding common mistakes, you can easily score full marks.

Focus on numericals, stay consistent, and you’ll master this chapter.

If you want to practice this topic, you can take a quiz in Curious Corner for better practice.