JEE Advanced 2020 Paper 2 – Electrostatics | Problem 5 Solution Explained

 

Introduction

Electrostatics is one of the most fundamental and high-weightage chapters in JEE Advanced Physics. Questions from this topic often test not only formula application but also deep conceptual clarity and analytical thinking. In this blog, we will break down JEE Advanced 2020 Paper 2 – Problem 5, a question that beautifully combines multiple electrostatic concepts.

If you are preparing for JEE Advanced, mastering such problems can significantly improve your rank and confidence.

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Understanding the Core Concept

Before jumping into the problem, it is important to recall the fundamental principle governing electrostatics — Coulomb’s Law.

$F = k \frac{q_1 q_2}{r^2}$

$q_1$

$q_2$

$r$

$F = k\frac{q_1 q_2}{r^2} \approx -5.06$

This law states that the force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

In advanced problems like this one, the challenge lies not in recalling the formula but in correctly applying it in multi-charge systems.

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Problem Overview

In JEE Advanced 2020 Paper 2, Problem 5 typically involves:

• Multiple charges placed in a specific configuration
• Interaction forces between charges
• Possibly constraints like equilibrium or net force conditions

Students often find this question tricky because it requires visualization and systematic breakdown.

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Step-by-Step Approach

1. Visualize the System

Start by carefully analyzing the given diagram. Identify:

• Number of charges
• Their positions
• Distances between them

Drawing a rough diagram on paper helps avoid mistakes.

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2. Identify Forces on Each Charge

For each charge, determine all the forces acting on it due to other charges.

Remember:

• Like charges repel
• Unlike charges attract

Each force acts along the line joining two charges.

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3. Resolve Forces (if needed)

If the charges are not aligned in a straight line, resolve forces into components:

• Horizontal (x-axis)
• Vertical (y-axis)

This step is crucial in 2D configurations.

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4. Apply Equilibrium Conditions

If the problem mentions equilibrium:

• Net force = 0
• Sum of forces in x-direction = 0
• Sum of forces in y-direction = 0

This gives you equations to solve unknown quantities.

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5. Solve Systematically

Substitute known values and solve step-by-step. Avoid skipping steps, especially in exam conditions.

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Common Mistakes to Avoid

• ❌ Ignoring direction of force
• ❌ Wrong sign convention (positive/negative charges)
• ❌ Not squaring the distance in Coulomb’s Law
• ❌ Skipping diagram visualization
• ❌ Calculation errors under time pressure

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Conceptual Insight

What makes this problem important is not just the answer, but the thinking process. JEE Advanced is designed to test how well you:

• Break down complex systems
• Apply fundamental laws
• Handle multi-step reasoning

Electrostatics problems often resemble puzzles — once you understand the structure, they become much easier.

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Exam Strategy Tips

• Always start with the simplest interaction first
• Write forces clearly with direction
• Use symmetry whenever possible
• Double-check units and powers

Time management is key — don’t get stuck on one step.

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Why This Problem Matters

Problem 5 from JEE Advanced 2020 Paper 2 is a perfect example of:

• Conceptual depth
• Multi-concept integration
• Real exam difficulty level

Practicing such problems prepares you for unpredictable and high-level questions.

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Conclusion

Electrostatics is not just about formulas — it’s about understanding interactions at a fundamental level. By mastering problems like JEE Advanced 2020 Paper 2 Problem 5, you build the confidence to tackle any challenging question in the exam.

Consistent practice, clear concepts, and smart strategies are the keys to success.

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I.E. Irodov Problem 3.29 | Electrostatics | Complete Solution

In this video, we solve I.E. Irodov Problem No. 3.29 from the chapter Electrostatics step by step in a simple and clear way. This problem is important for building strong concepts in electric fields and charge distribution, especially for competitive exams like JEE Advanced, NEET, and олимпиad-level physics. 🔍 What you will learn: Conceptual understanding of electrostatics Step-by-step problem-solving approach Important formulas and tricks How to tackle similar Irodov problems 🌐 Visit: physicsonlinetutor.com 📞 Contact: 9811767502

   

Master JEE Advanced 2022 Question 13 from the chapter Electrostatics with this clear

In this video, we break down the concept step-by-step so that you not only solve the problem but truly understand the physics behind it. This question is very important for JEE aspirants as it covers key electrostatics concepts frequently asked in exams. Make sure to watch till the end to strengthen your problem-solving approach. 🔴 What you will learn: Conceptual approach to Electrostatics problems Step-by-step solution of Question 13 Tricks to solve similar JEE Advanced questions Common mistakes to avoid 🌐 Visit our website for more content: 👉 physicsonlinetutor.com 📞 For personal guidance & coaching: 👉 Call/WhatsApp: 9811767502 📚 We provide: JEE Advanced & NEET Physics Coaching Small batch & individual classes Assignments, tests & study material 👍 If you found this helpful, don’t forget to: Like 👍 Share 📤 Subscribe 🔔 for more JEE Advanced PYQ solutions #JEEAdvanced2022 #Electrostatics #Physics #JEEMains #JEEPreparation #PhysicsOnlineTutor

 

JEE Advanced 2023 PYQ | Electrostatics | Problem 1 Solution | By Shivendra Sir

Introduction

Hello aspirants! If your goal is cracking JEE Advanced, then solving and deeply understanding past year questions is non-negotiable. These problems reveal the mindset of IIT examiners and train you to think beyond formulas.

In this article, we will break down JEE Advanced 2023 Electrostatics Problem 1 (Paper 2)—a question that beautifully blends vector concepts with electrostatics. At first glance, it may seem tricky due to coordinate changes, but once approached logically, it becomes surprisingly simple.

As always, remember the core philosophy: understand the physics first, then apply the math.

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Problem Overview

We are given an electric dipole formed by charges +q and –q placed at specific coordinates. The electric potential at a distant point P is given as $V_0$V0​. Then, the charges are shifted to new positions, and we are asked to find the new potential at the same point.

This is not just a formula-based question—it tests your understanding of:

• Dipole moment direction
• Vector representation
• Approximation techniques

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Concepts You Must Know

To solve this problem efficiently, you need clarity on the following:

1. Short Dipole Approximation

When the observation point is far away compared to the separation of charges, the dipole behaves like a “point dipole.” This simplifies calculations significantly.

2. Potential Due to a Dipole (Vector Form)

Instead of using angle-based formulas, we use the vector form:

$V=\frac{k(\vec{p}\cdot \vec{r})}{r^3}$V=r3k(p​⋅r)​

This is faster and reduces calculation errors.

3. Dipole Moment Definition

The dipole moment vector always points:

• From negative charge to positive charge
• Magnitude = charge × separation

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Step-by-Step Solution

Let’s divide the problem into two parts: initial configuration and final configuration.

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Initial Configuration

Step 1: Identify Charge Positions

• Negative charge at (0, –2) mm
• Positive charge at (0, 2) mm

Clearly, the dipole lies along the y-axis.

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Step 2: Dipole Moment Vector

The displacement from negative to positive charge is along +y direction:$${\vec{p}}_1=q\cdot (4\widehat{j})$$p​1​=q⋅(4j^​)

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Step 3: Position Vector of Point P

Point P is at (100, 100) mm:$$\vec{r}=100\widehat{i}+100\widehat{j}$$r=100i^+100j^​

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Step 4: Calculate Initial Potential

Using the dot product:$${\vec{p}}_1\cdot \vec{r}=q(4\widehat{j})\cdot (100\widehat{i}+100\widehat{j})$$p​1​⋅r=q(4j^​)⋅(100i^+100j^​)

Only the $\widehat{j}\cdot \widehat{j}$j^​⋅j^​ term contributes:$$=4q\times 100=400q$$=4q×100=400q

So,$$V_0=\frac{k\cdot 400q}{r^3}$$V0​=r3k⋅400q​

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Final Configuration

Now the charges are shifted:

• Negative charge → (1, –2) mm
• Positive charge → (–1, 2) mm

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Step 5: New Dipole Moment

Calculate displacement from –q to +q:

• x-direction: –1 – 1 = –2
• y-direction: 2 – (–2) = 4

So,$${\vec{p}}_2=q(-2\widehat{i}+4\widehat{j})$$p​2​=q(−2i^+4j^​)

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Step 6: Compute New Potential

$${\vec{p}}_2\cdot \vec{r}=q(-2\widehat{i}+4\widehat{j})\cdot (100\widehat{i}+100\widehat{j})$$p​2​⋅r=q(−2i^+4j^​)⋅(100i^+100j^​)$$=(-2\times 100)+(4\times 100)$$=(−2×100)+(4×100)$$=-200+400=200$$=−200+400=200

Thus,$$V_{\text{new}}=\frac{k\cdot 200q}{r^3}$$Vnew​=r3k⋅200q​

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Final Result

Comparing both:

• Initial potential = $\frac{400kq}{r^3}$r3400kq​
• New potential = $\frac{200kq}{r^3}$r3200kq​

Hence,$$V_{\text{new}}=\frac{V_0}{2}$$Vnew​=2V0​​

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Important Insights

This problem teaches a powerful lesson:

• The magnitude of dipole moment alone doesn’t determine potential
• Direction relative to position vector matters equally

The reduction to half occurs due to the change in orientation of the dipole.

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Common Mistakes Students Make

1. Ignoring Vector Method

Using trigonometry here wastes time and increases error chances.

2. Wrong Dipole Direction

Always remember: negative → positive.

3. Overcomplicating the Problem

Many students try full charge potential calculation instead of using dipole approximation.

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Exam Strategy

• Look for symmetry and approximation opportunities
• Always convert geometry into vectors
• Use dot product for faster calculation
• Avoid unnecessary expansions

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Why This Question Matters

This is a classic JEE Advanced level conceptual problem because it checks:

• Vector clarity
• Physical understanding
• Application of approximation

If you can solve such problems confidently, you are on the right track for a top rank.

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Conclusion

The JEE Advanced 2023 Electrostatics Problem 1 highlights the importance of thinking in vectors rather than blindly applying formulas. With the right approach, even complex-looking problems become manageable.

Practice more such PYQs and focus on understanding the why behind each step. That’s the real key to mastering Physics.

Keep learning, stay consistent, and trust the process.

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JEE Advanced 2025 | Question 14 Solution | Electrostatics

we solve JEE Advanced 2025 Question 14 from the chapter Electrostatics in a clear and step-by-step manner. This question is very important for students preparing for IIT JEE Advanced, as it covers key concepts like electric force, Coulomb’s law, and charge interaction. 📘 What you will learn in this video: Conceptual understanding of Electrostatics Application of Coulomb’s Law Step-by-step problem-solving approach Tips to solve similar JEE Advanced questions faster 🎯 This video is बेहद useful for: Class 11 & 12 Physics students JEE Main & Advanced aspirants Students preparing for competitive exams like NEET 🌐 Join our online classes: 👉 Website: www.physicsonlinetutor.com 📞 Call/WhatsApp: 9811767502 💡 Why choose us? Experienced Physics faculty Concept-based teaching Regular problem practice sessions व्यक्तिगत ध्यान (Personal attention) 📌 Important Topics Covered: Electrostatics, Electric Force, Coulomb’s Law, Charge Interaction

I.E. Irodov Problem No. 3.25 Solution | Electrodynamics Explained for JEE Advanced

 

Frequently Asked in Exams

Concepts from this problem are often used in:

• JEE Advanced
• NEET Physics
• Olympiad exams

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 3. Base for Advanced Topics

This concept is useful in:

• Charged particle motion
• Electrostatics applications
• Electrodynamics problems

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 How to Solve Similar Problems

Follow this step-by-step approach:

1. Identify all forces acting on the particle
2. Write mathematical expressions for each force
3. Compare magnitudes of forces
4. Apply condition (greater than / equal / less than)
5. Solve for required variable

 This method works for almost all force comparison problems.

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 Common Mistakes to Avoid

• Ignoring direction of forces
• Not applying inequality correctly
• Confusing equilibrium with motion
• Missing units or incorrect substitution

 Always double-check your force comparison.

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 Pro Tips for JEE Advanced

• Questions may include inclined planes or multiple forces
• Electric field direction may be tricky
• Sometimes acceleration is asked instead of condition

 Practice variations to master the concept.

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 Learn Physics with Expert Guidance

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Pathfinder Physics | Building Up Problem No. 7 Solution Electric Current

In this video, we solve Pathfinder Building Up Problem No. 7 from the chapter Electric Current in a clear and step-by-step manner. This problem is very important for JEE Advanced / Olympiad preparation, and understanding it will strengthen your concepts of current flow, resistance, and circuit analysis. 🔍 What you will learn: Conceptual approach to Electric Current problems Shortcut techniques for faster solving Common mistakes to avoid in exams Complete detailed explanation for better clarity 📘 This is part of the Pathfinder Physics series, specially designed to build strong fundamentals and problem-solving skills. 🌐 Website: physicsonlinetutor.com 📞 Contact: 9811767502 💡 If you want to master Physics for JEE Advanced, make sure to watch the full video and practice regularly. 👍 Like | 🔔 Subscribe | 📢 Share with friends #PathfinderPhysics #ElectricCurrent #JEEAdvanced #PhysicsSolution #IITJEE #PhysicsTutor