← (ne09) Drawing Q, E & V →

4.再探討電荷與電場
Fields and Potentials	Hand-Draw Line Charges	Hand-Draw Components

Key Concepts

Electric field (E) Lines

1. Start at a positive (+) charge
2. End at a negative (−) charge
3. Separation between lines reflects the strength of the field.
   (closer together → stronger field)
4. Electric Field (E) lines must have arrows to show direction

Equi-Potential Surfaces (3D), Lines (2D) (V=constant)

1. No direction
2. Perpendicular (⟂) to E
3. Potential at infinity set to zero (V(∞)=0).
4. closer together → more rapid ΔV, higher E

Steps in Using Simulation

1. Place charges on the screen.
2. Observe the e-field vectors
3. Use the tool to draw equi-potential lines with constant ΔV
4. Write the value of the potential (V=??) on each line
5. Add sensors (+ test charge) to show the electric field vectors.
6. Draw the electric field

Facilitating Videos ‐ Guiding you as you practice on YouTube

Drawing Q, E and V Diagrams (Part 1)
In this series of videos, the student is guided in the drawing of Electric field lines and equipotential surfaces for a variety of charge distributions starting with single isolated charges, dipoles, ion traps, lines of charges and finally antennas.   
In viewing, please follow along on http://www.aizhu.com/xiaotu/tea/physics/ne09.htm.

NOTE: These videos make use of the HTML5 PHeT simulation "charges-and-fields".

1. Introduction, Single Charges, Preparing to Solve for Dipoles
2. Dipoles to Line of Charge
3. Lines of Charges to Batteries and Antennas
4. Antennas -- Q, V, E and Light!

Practice (Use PhET Simulation as Aid)

Fill in Hand-out

1. Using the simulation as an aid, please complete electric field (E) and equi-potential (V=const) lines for each of the pictures.
2. Hand in at the begining of next class if you cannot finish in class.

Basic Single Charges


1. single positive (+)
2. single negative (−)
3. dipole (+ & −)
4. two positive (+)
5. triangle of positive (+)
6. square of positive (+) charges (+ ion trap)

Lines of Charges


1. line of negative (−) charge
2. line of charge + single negative (−) charge
3. line of charge + single positive (+) charge

Batteries, Antennas, Capacitors


1. battery
2. battery with wire
3. battery with antenna, broken circuit
4. battery with antenna,complete circuit