Electrical Force: Definition, Types, and Coulomb’s Law

Electric force is the interaction of attraction or repulsion between charged particles. It is governed by Coulomb’s law and plays a central role in physics, chemistry, and daily life. This page covers the definition of electric force, its formula, types (attractive/repulsive), real-world examples, and a comprehensive FAQ section for exams and interviews.

What is Electric Force?

• Definition: Electric force is the force of attraction or repulsion between two charged bodies. It acts along the line joining the charges.
• Nature: Vector quantity (has both magnitude and direction).
• Acts between: Charged particles (protons, electrons, ions, etc.), regardless of mass.

Coulomb’s Law and Electric Force Formula

Coulomb’s Law: The magnitude of the electrostatic force (F) between two stationary point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

• If both charges are of the same sign (both positive or both negative), the force is repulsive.
• If the charges are of opposite sign, the force is attractive.

Types of Electric Forces

• Attractive Force: Occurs between opposite charges (+ and -).
• Repulsive Force: Occurs between like charges (+ and +, or - and -).
• Electrostatic Force: Electric force between stationary charges.
• Dynamic/Electrodynamic Force: Electric force involving moving charges (currents).

Examples of Electric Force in Daily Life

• Static electricity causing hair to stand up after removing a hat
• Shocks from touching a metal doorknob
• Lightning (attraction between clouds and ground)
• Electric circuits powering a bulb
• Electrostatic paint spraying and photocopiers
• Forces between protons and electrons in atoms

Charge Interactions: Attraction and Repulsion

Electric Force and Charged Particles

• Protons (positive charge) and electrons (negative charge) are subatomic particles inside atoms.
• Imbalance in the number of electrons and protons makes an object charged.
• Electrons are mobile and can move, creating static or current electricity.
• Protons are fixed in the nucleus and do not move freely.

Frequently Asked Questions (FAQs) about Electric Force

1. What is electric force?
   Electric force is the force of attraction or repulsion between two charged objects, governed by Coulomb’s law.
2. How do electric forces work?
   Like charges repel each other, while unlike charges attract each other.
3. What is the formula for electric force?
   F = k × |q₁ × q₂| / r², where q₁ and q₂ are charges, r is distance, and k is Coulomb’s constant.
4. What are the two types of electric force?
   Attractive force (opposite charges) and repulsive force (like charges).
5. What is electrostatic force?
   The force between stationary charges, described by Coulomb’s law.
6. How is electric force different from gravitational force?
   Electric force acts between charges and can attract or repel, while gravity always attracts and acts on mass.
7. Where is electric force used in daily life?
   In static electricity, electronic devices, photocopiers, painting, and many industrial processes.
8. Does distance affect electric force?
   Yes, electric force decreases rapidly as distance increases (inversely with the square of the distance).
9. What is Coulomb’s law and why is it important?
   Coulomb’s law quantifies electric force and is fundamental in understanding electricity, electronics, and atomic structure.
10. Is electric force a contact or non-contact force?
    It is a non-contact force; it acts over a distance without physical contact.
11. How can you measure electric force?
    Using sensitive electronic instruments (like electroscopes) or by calculating with Coulomb’s law.
12. Can electric force act on neutral objects?
    Yes, through induction or polarization, charged objects can attract neutral objects (e.g., paper bits attracted to a charged comb).
13. What is the SI unit of electric force?
    Newton (N).
14. Why is electric force stronger than gravitational force?
    For subatomic particles, the electric force is vastly stronger than gravity (about 10³⁶ times for an electron-proton pair).
15. Can electric force be shielded?
    Yes, using conductors (Faraday cage) or grounded enclosures.

Practice MCQs: Electric Force and Coulomb’s Law

1. What is the SI unit of electric force?
   a) Coulomb
   b) Newton
   c) Joule
   d) Volt
2. Which law gives the quantitative value of the electric force between two point charges?
   a) Newton’s law
   b) Ohm’s law
   c) Coulomb’s law
   d) Faraday’s law
3. Two like charges placed close to each other will:
   a) Attract each other
   b) Repel each other
   c) Remain unaffected
   d) Lose charge
4. What happens to the electric force between two charges if the distance between them is doubled?
   a) It doubles
   b) It becomes four times
   c) It is reduced to half
   d) It is reduced to one-fourth
5. If the charges on both particles are doubled, the electric force between them becomes:
   a) Double
   b) Half
   c) Four times
   d) Unchanged
6. Which of the following pairs will experience an attractive electric force?
   a) Electron and proton
   b) Electron and electron
   c) Proton and proton
   d) Two neutral atoms
7. The value of Coulomb’s constant (k) in SI units is:
   a) 9 × 10⁹ N·m²/C²
   b) 6.67 × 10^-11 N·m²/kg²
   c) 1.6 × 10^-19 C
   d) 3 × 10⁸ m/s
8. The force between two charges q₁ and q₂ separated by distance r is proportional to:
   a) q₁q₂
   b) 1/r
   c) 1/r²
   d) q₁ + q₂
9. The force of attraction or repulsion between two charges acts:
   a) Only when they touch
   b) At a distance (non-contact force)
   c) Only in vacuum
   d) Only when grounded
10. What happens to the electric force if both charges are positive?
    a) Force is attractive
    b) Force is repulsive
    c) Force is zero
    d) None of the above

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