THE PRACTICE STUDIO
Go slowly. Ask why. Make it yours.
PRACTICE / Electric flux
Flux through an enclosing surface
A closed surface encloses net charge +3 nC. Use ε₀ = 8.85 × 10⁻¹² F/m.
Find the outward electric flux.
Organize the givens & assumptions
- Qenc = 3×10⁻⁹ C
- ε₀ = 8.85×10⁻¹² F/m
Electrostatic field in vacuum; closed surface; use ε₀ = 8.85 × 10⁻¹² F/m; only net enclosed charge sets total flux.
Study with a tutor prompt
Copy this into your AI assistant, then describe where you got stuck. It asks the tutor to coach you one step at a time. Check its reasoning against the lesson.
Opening this prompt marks this practice attempt as assisted.
Problem: Flux through an enclosing surface
A closed surface encloses net charge +3 nC. Use ε₀ = 8.85 × 10⁻¹² F/m.
Question: Find the outward electric flux.
Givens:
- Qenc = 3×10⁻⁹ C
- ε₀ = 8.85×10⁻¹² F/m
Assumptions: Electrostatic field in vacuum; closed surface; use ε₀ = 8.85 × 10⁻¹² F/m; only net enclosed charge sets total flux.
Choices (LaTeX):
A. 33.9\ \mathrm{N\,m^2/C}
B. -339\ \mathrm{N\,m^2/C}
C. 339\ \mathrm{N\,m^2/C}
D. 0
Ask for my approach first. Help me distinguish a physical misconception from an algebra error without revealing which choice is correct.
Tutoring approach:
Act as a patient physics tutor. Ask what I understand and what I have tried, then wait for my reply. Teach one step at a time; do not give the final answer or a complete solution immediately. Start with a physical picture. Define unfamiliar symbols and operators, explain signs and units, and state the model's assumptions. Give progressively stronger hints only when I need them. Ask me to predict a change before calculating it. When I finish, help me check dimensions and a limiting case, then ask one related transfer question. If information is missing or ambiguous, ask rather than inventing it. Distinguish exact results from approximations and acknowledge uncertainty.Start with the smallest hint.
Work through it with me.
One decision at a time. Pause, predict, then unpack the algebra.
Only enclosed net charge determines the total flux; the surface shape does not enter.
Choose a physical relation
Gauss's law links total outward flux through a closed surface to algebraic charge enclosed by that surface.
Isolate what is asked
Only enclosed net charge determines the total flux; the surface shape does not enter.
Why is this step valid?
Divide charge in coulombs by ε₀; external charges may change local fields but not this net flux.
Substitute and interpret
Positive enclosed charge gives positive net outward flux; no spherical symmetry is required for that conclusion.
One nanocoulomb gives about 113 N·m²/C of flux in vacuum; three nanocoulombs gives three times that, outward for positive charge. Shrinking or deforming the surface without crossing the charge cannot alter it.
TRY THE IDEA AGAIN
Enclose equal positive and negative charges. Must the field be zero everywhere on the surface?
YOUR LEARNING NOTE
How does this idea feel now?
Confidence is a reflection, not proof of mastery.
Loading… · 0 answer checks
Loading your learning note…