Question 1

What is Coulomb's law?

Accepted Answer

Coulomb's law describes the electrostatic force between two charged particles. It 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. The formula is F = k × |q₁ × q₂| / r², where k is Coulomb's constant (8.99 × 10⁹ N⋅m²/C²), q₁ and q₂ are the charges, and r is the distance between them.

Question 2

What is the formula for Coulomb's law?

Accepted Answer

The electrostatic force formula is F = k × |q₁ × q₂| / r², where F is the force in newtons, k = 8.99 × 10⁹ N⋅m²/C² is Coulomb's constant, q₁ and q₂ are the charges in coulombs, and r is the distance in meters. The electric field formula is E = k × |q| / r², and the potential energy formula is U = k × q₁ × q₂ / r. The force is attractive for opposite charges and repulsive for like charges.

Question 3

How do you calculate electric field from Coulomb's law?

Accepted Answer

The electric field at a point due to a charge q is calculated using E = k × |q| / r², where k is Coulomb's constant, q is the source charge, and r is the distance from the charge. The electric field is a vector quantity pointing away from positive charges and toward negative charges. For multiple charges, use the principle of superposition: E_total = E₁ + E₂ + E₃ + ... (vector addition).

Question 4

What are the key properties of Coulomb's law?

Accepted Answer

Key properties include: 1) Inverse square law - force decreases as 1/r², 2) Proportional to charge product - force increases with charge magnitude, 3) Conservative force - work done is path-independent, 4) Superposition principle - total force is vector sum of individual forces, 5) Like charges repel, opposite charges attract, 6) Valid for point charges or spherically symmetric charge distributions, 7) Fundamental to understanding electrostatics and electromagnetic interactions.

Question 5

What are real-world applications of Coulomb's law?

Accepted Answer

Common applications include: 1) Capacitor design - calculating electric fields and forces between plates, 2) Particle accelerators - understanding charged particle interactions, 3) Electrostatic precipitators - removing particles from air using electric fields, 4) Inkjet printers - controlling charged ink droplets, 5) Van de Graaff generators - building up static charge, 6) Lightning formation - understanding charge separation in clouds, 7) Atomic structure - electron-nucleus interactions, 8) Molecular bonding - understanding ionic and covalent bonds.

Question 6

How do you interpret Coulomb's law results?

Accepted Answer

Interpretation depends on the calculation type: F (force) tells you the magnitude of electrostatic force between charges. E (electric field) shows the force per unit charge at a point. U (potential energy) indicates the energy stored in the charge configuration. Positive force means repulsion (like charges), negative means attraction (opposite charges). Higher charges or closer distances result in stronger forces. The force is always along the line connecting the charges.

Question 7

What's the difference between Coulomb's law and Newton's law of gravitation?

Accepted Answer

Both are inverse square laws, but key differences include: Coulomb's law involves electric charges (can be positive or negative), while gravitation involves mass (always positive). Coulomb's constant (k) is much larger than gravitational constant (G), making electrostatic forces much stronger. Coulomb's law can be attractive or repulsive, while gravitation is always attractive. Coulomb's law applies to charged particles, while gravitation applies to all masses. Both follow the same mathematical form: F ∝ (property₁ × property₂) / r².

Question 8

How do you use Coulomb's law for problem solving?

Accepted Answer

Problem-solving steps include: 1) Identify all charges and their positions, 2) Choose appropriate formula (force, field, or energy), 3) Convert units to SI (coulombs, meters), 4) Calculate individual forces/fields, 5) Use vector addition for multiple charges, 6) Consider symmetry to simplify calculations, 7) Check units and reasonableness of results, 8) Apply boundary conditions if needed. For complex geometries, use integration or numerical methods. Always consider the direction of forces and fields.

Question 9

What are common mistakes when using Coulomb's law?

Accepted Answer

Common mistakes include: 1) Forgetting to square the distance in the denominator, 2) Not using absolute values for charges in force calculations, 3) Confusing force, field, and potential energy formulas, 4) Ignoring vector nature of forces and fields, 5) Not converting units properly (especially microcoulombs to coulombs), 6) Forgetting that like charges repel and opposite charges attract, 7) Not considering superposition for multiple charges, 8) Using wrong sign conventions for potential energy.

Question 10

How do you calculate Coulomb's law with multiple charges?

Accepted Answer

For multiple charges, use the superposition principle: 1) Calculate the force/field due to each individual charge, 2) Use vector addition to find the total force/field, 3) For forces: F_total = F₁ + F₂ + F₃ + ... (vector sum), 4) For electric fields: E_total = E₁ + E₂ + E₃ + ... (vector sum), 5) For potential energy: U_total = U₁₂ + U₁₃ + U₂₃ + ... (scalar sum), 6) Consider symmetry to simplify calculations, 7) Use components (x, y, z) for vector addition, 8) Apply Coulomb's law to each pair of charges separately.

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