Section 1.4: Superposition Principle
The superposition principle states that the net force on a charge is the vector sum of all individual forces exerted on it by other charges.
Superposition Principle:
\( \vec{F}_{\text{net}} = \sum_i \vec{F}_i \)
Each \( \vec{F}_i \) is calculated using Coulomb’s law for the respective pair of charges.
Example 1
Three charges form a triangle. Compute net force on \( q_1 \) using vector addition.
Compute \( \vec{F}_{12} \) and \( \vec{F}_{13} \) separately and add vectors: \( \vec{F}_{\text{net}} = \vec{F}_{12} + \vec{F}_{13} \).
Practice Problems
- Two charges along x-axis, one at origin and one at x=0.5 m. Find net force on a third charge placed at x=0.25 m.
- Four charges at corners of a square: calculate net force on one charge.
- Three charges on a line. Determine the net force on the middle charge.
- Explain why superposition allows solving complex configurations analytically.
- Vector diagram practice: add two non-collinear forces.