Electric field of a point charge
7 flashcards to master this topic
State the formula for the electric field strength (E) due to a point charge (Q) in free space.
E = Q / (4πε₀r²), where E is the electric field strength, Q is the magnitude of the point charge, ε₀ is the permittivity of free space, and r is the distance from the charge.
Describe how the electric field strength (E) due to a point charge changes with increasing distance (r) from the charge.
The electric field strength (E) is inversely proportional to the square of the distance (r) from the point charge. Therefore, as distance increases, the electric field strength decreases rapidly (E ∝ 1/r²).
A +5.0 nC point charge is placed in a vacuum. Calculate the electric field strength at a distance of 2.0 cm from the charge. (ε₀ = 8.85 × 10⁻¹² F m⁻¹)
E = Q / (4πε₀r²) = (5.0 × 10⁻⁹) / (4π × 8.85 × 10⁻¹² × (0.02)² ) ≈ 1.12 × 10⁵ N C⁻¹
What are the units for electric field strength (E) when calculated using E = Q / (4πε₀r²)?
The units for electric field strength (E) are Newtons per Coulomb (N C⁻¹).
How does the sign of the point charge (Q) affect the direction of the electric field it produces?
A positive point charge produces an electric field that points radially outward from the charge. A negative point charge produces an electric field that points radially inward towards the charge.
Two identical +10 nC point charges are separated by 4 cm. Determine the electric field strength at the midpoint between the charges.
The electric fields due to each charge are equal in magnitude but opposite in direction at the midpoint. Therefore, the net electric field strength at the midpoint is zero.
Define permittivity of free space (ε₀).
Permittivity of free space (ε₀) is a physical constant that quantifies the ability of a vacuum to permit electric fields. It appears in many equations relating to electromagnetism and has an approximate value of 8.85 × 10⁻¹² F m⁻¹.
Ready to test yourself?
Practice with MCQ questions to check your understanding of Electric field of a point charge.
Take QuizStudy Mode
Rate each card Hard, Okay, or Easy after flipping.