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Topic Overview
- The study of the electric force between point charges, defined as Coulomb's Law.

State Coulomb’s Law.
Explain the relation between electric force and the magnitude and distance of point charges.
Solve problems involving electrostatic forces using Coulomb’s Law.

Relationship to Coulomb's Law:
- Devoted his life to studying charges.
- Discovered a method to calculate the electric force of a point charge using Coulomb’s torsion balance.
- Unit of charge: Coulombs (C), named after him.
- Introduced the Coulomb’s Law and its equation.

Formula: $F = k \frac{|q<em>1 q</em>2|}{r^2}$
- Where:
- F: Electric Force (N)
- q1: Point charge 1 (C)
- q2: Point charge 2 (C)
- r: Distance between the two charges (m)
- k: Coulomb’s constant (approximately $9.0 \times 10^9 \text{ Nm}^2/\text{C}^2$ ).

Proportionality:
- Electric Force is directly proportional to the magnitude of the point charges and inversely proportional to the distance between the point charges.

Exercise 1:
- Two objects, charges +1.0 C and -1.0 C, are 1.0 km apart.
- Calculation:
- Magnitude of attractive force: $F = 9.0 \times 10^3 N$ .
Exercise 2:
- A charge of +10μC is 25 cm from -20μC.
- Calculation:
- Electric force magnitude: $F = 30 N$ .
Exercise 3:
- Electric force between +800nC and +900nC is 15.0 N.
- Calculation:
- Distance: $r = 0.02m ext{ or } 2\times 10^{-2} m$ .
Exercise 4:
- Electrostatic force between 2.0 C and -1.0 C separated by 1.0 m:
- Calculation:
- Force: $F = 1.8 \times 10^{10} N$ .
Exercise 5:
- Charges of 2 × 10^-7 C and 4.5 × 10^-7 C acted on by 0.1 N.
- Calculation:
- Distance: $r = 9 \times 10^{-2} m$ .
Exercise 6:
- Identical charges with electrostatic force of 1000 N, separated by 0.01 m.
- Calculation:
- Charge magnitude: $3 \times 10^{-6}C ext{ or } 3µC$ .

Definition:
- An electric field is a region around charged particles where other charged particles feel a force.
- Denoted by E, it causes any charge within it to experience an electric force.
- Every charge has an electric field associated with it.

Definition of Electric Field Lines:
- Imaginary lines drawn to show the direction of the electric field at any point; tangent at any point represents the electric field vector.

Direction:
- Away from positive charges and toward negative charges.
Starting and Ending Points:
- Start from positively charged particles and end on negatively charged particles or extend towards infinity.
Line Behavior:
- Field lines do not intersect or break.
Density:
- Field strength is indicated by the number of lines; closer lines indicate stronger fields.

Test Charge Method:
- Electric field (E) is defined as the force experienced by a test charge situated at that point.
- Formula:
  $E = \frac{F}{q_0}$
- Where:
  - E: Electric Field (N/C)
  - F: Electric Force
  - q0: Test charge.
Coulomb's Calculation for Electric Field:
- $E = k \frac{q}{r^2}$
- Where q is the point charge, r is the distance from the charge.

Exercise on Electric Field:
- Calculate electric fields resulting from point charges using previously discussed values and equations.

Definition:
- Electric flux indicates the amount of electric field lines passing through a surface.
- It is calculated as the dot product of the electric field and the area:
  $\Phi_E = E imes A imes \cos(\Theta)$
- Where:
  - Φ_E: Electric Flux (Nm²/C)
  - E: Electric Field (Nm)
  - A: Surface Area (m²)
  - Θ: Angle between the electric field and area vector.

Determine the electric flux through surfaces in various orientations to electric fields.

Introduction:
- Introduced by Carl Friedrich Gauss in 1835, relates electric fields at points on a closed surface to the net charge enclosed.

Formula for Gauss's Law: $\Phi<em>E = \frac{q}{\epsilon</em>0}$
- Where ε₀ is the permittivity of free space (≈ 8.85 x 10^-12 C²/Nm²).

Calculate electric flux for various charge configurations using the established equations.

The concepts of Coulomb’s Law, Electric Fields, and Gauss's Law are foundational to understanding electrostatics, providing insight into both theoretical calculations and practical applications in electrical engineering and physics.