Coulomb's Law Calculator for Class 12 Physics Students

Coulomb's Law Calculator

Calculate Electrostatic Force Instantly with Step-by-Step Solutions

Enter Values

Charge 1 (q₁)

C (Coulombs) mC (Milli) μC (Micro) nC (Nano)

Charge 2 (q₂)

C (Coulombs) mC (Milli) μC (Micro) nC (Nano)

Distance between charges (r)

m (Meters) cm (Centimeters) mm (Millimeters)

Please enter valid numbers for all fields. Distance cannot be zero.

Step-by-Step Solution

👉 How to Use This Calculator

1. Enter Charge 1 (q₁): Input the numerical value of the first charge. Use the dropdown to select the unit (Coulombs, microCoulombs, etc.).
2. Enter Charge 2 (q₂): Input the numerical value of the second charge. It can be positive or negative.
3. Enter Distance (r): Input the straight-line distance between the centers of the two charges. Note: Distance cannot be zero!
4. Click "Calculate Force": The calculator will automatically generate the final electrostatic force along with a detailed step-by-step CBSE-style breakdown.

Coulomb’s Law: Comprehensive Study Guide (Class 12 Physics)

Understanding the fundamental forces of nature is the core of Physics. In Class 12 CBSE and NCERT syllabus, Chapter 1 (Electric Charges and Fields) introduces us to the invisible yet immensely powerful electrostatic force. Whether you are preparing for board exams, JEE, or NEET, mastering Coulomb's Law is your very first step into the world of Electromagnetism.

What is Coulomb's Law? (Definition & Formula)

Formulated by French physicist Charles-Augustin de Coulomb in 1785, Coulomb's Law quantifies the amount of force between two stationary, electrically charged particles. This force is often called the electrostatic force or Coulomb force.

Statement: The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.

F = k × (|q₁| × |q₂|) / r²

Where:

• F = Electrostatic Force (measured in Newtons, N)
• q₁, q₂ = Magnitudes of the interacting charges (measured in Coulombs, C)
• r = Distance separating the centers of the charges (measured in meters, m)
• k = Coulomb's constant or electrostatic constant, approximately 8.98755 × 10⁹ N·m²/C² in a vacuum.

💡 Did You Know?
Charles Coulomb discovered this law using a delicate instrument called a torsion balance. He didn't have digital multimeters! He relied on the twist of a fine thread to measure incredibly tiny electrostatic forces.

Mathematical Explanation & The Constant 'k'

The constant k is not just a random number. It is derived from the properties of the medium separating the charges, expressed mathematically as:

k = 1 / (4 π ε₀)

Here, ε₀ (epsilon naught) is the permittivity of free space (vacuum), which has a value of roughly 8.854 × 10^-12 C²/(N·m²). If the charges are placed in a different medium (like water or oil), the force decreases because the medium's permittivity (ε) is higher than that of a vacuum.

Note: Our calculator above computes the force assuming the charges are in a vacuum or air.

Real-Life Examples and Applications

While point charges sound like abstract textbook concepts, Coulomb's Law explains phenomena we experience daily:

• Static Cling: When you take clothes out of a dryer, they stick together. The friction transfers electrons, giving pieces of clothing opposite charges that attract each other according to Coulomb's Law.
• Photocopiers and Laser Printers: These machines use electrostatic attraction. A charged drum attracts toner particles (which have an opposite charge) exactly where the text or image needs to be printed.
• Atomic Structure: The very reason you exist! The electrostatic force of attraction between the positively charged nucleus (protons) and negatively charged electrons keeps atoms intact.
• Powder Coating: In manufacturing, paint powder is given a positive charge and sprayed onto a negatively charged grounded metal object, ensuring an even, perfectly adhering coat.

Common Misconceptions About Electric Force

• Misconception 1: "A larger charge exerts a larger force on a smaller charge."
  Reality: According to Newton's Third Law and Coulomb's Law, the forces are equal and opposite. If a 10 C charge interacts with a 1 C charge, the 10 C charge pulls the 1 C charge with the exact same amount of force that the 1 C charge pulls the 10 C charge.
• Misconception 2: "The force disappears if a third charge is introduced."
  Reality: The force between any two specific charges remains unaffected by the presence of a third charge. This is known as the Principle of Superposition. The *net* force on a charge will change, but the individual pairwise forces do not.

🧠 Quick Concept Check (CBSE Style)

• Q1: What happens to the electrostatic force if the distance between two charges is doubled? Answer: Since F is inversely proportional to the square of the distance (1/r²), doubling the distance (2r) makes the force 1/4th of its original value.
• Q2: Is Coulomb force a central force? Answer: Yes. The electrostatic force always acts along the straight line joining the centers of the two charges.
• Q3: How does the force change if the charges are immersed in water? Answer: The force decreases drastically. Water has a high dielectric constant (approx 81), so the force becomes 1/81 times the force in a vacuum.

Summary

Coulomb's Law is the bedrock of electrostatics. Remember that "Like charges repel, and unlike charges attract." By using our Coulomb's Law Calculator, students can quickly verify their homework, understand the step-by-step substitution of powers of 10, and avoid common calculation errors related to units like microCoulombs or centimeters.

You May Also Like

Loading...