Week4 3Wed ph 213 2015 - Lecture note Week 4 - 3 PDF

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Download Week4 3Wed ph 213 2015 - Lecture note Week 4 - 3 PDF

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QuickCheck 29.7 A particle follows the trajectory shown from initial position i to final position f. The potential difference ∆V is A. B. C. D. E.

100 V. 50 V. 0 V. −50 V. −100 V.

Slide 29-54

QuickCheck 29.7 A particle follows the trajectory shown from initial position i to final position f. The potential difference ΔV is A. B. C. D. E.

100 V. 50 V. 0 V. −50 V. −100 V.

∆V = Vfinal – Vinitial, independent of the path

Slide 29-55

Questions • • • •

How can we create an electric potential? How can we relate V to E geometrically? Mathematically? Fundamentally what creates a potential difference? What are different ways we use energy to generate a potential difference?

How to create an electric potential difference (voltage)? • Mechanically • Chemically • Electromagnetically

How to create an electric potential difference? • Mechanically • Chemically • Electromagnetically

Mechanically Van de Graaff generator

Chemically • Electrodes and electrolytes

https://www.youtube.com/watch?v=0TvYlJ06MXo https://www.youtube.com/watch?v=HhxtfULIO7c

Chemically

Chemically

Batteries and emf • #

Electromagnetically

Charged capacitor

Which electric potential graph describes this electric field?

A. B. C. D. E.

Which electric potential graph describes this electric field?

*Flip graph about the horizontal axis.

Potential, potential energy, force, electric field

FC

UC U C = qV

FC = qE

E

V

One dimension – two examples dV ∆V = − E∆x ⇒ E = − dx The component of E along the path travelled contributes to the change in electric potential along the path.

Potential and field   V2 − V1 = −∫ E ⋅ dr 2

1

Potential and field dV ∆V = − E∆x ⇒ E = − dx

Which set of equipotential surfaces matches this electric field?

1

2

4

3

5

21

Which set of equipotential surfaces matches this electric field?

1

2

4

3

5

22

Which E-vector is correct??

A

B

C

0V

-10V

D

-20V

-30V

Which E-vector is correct??

A

B

C

0V

-10V

D

-20V

-30V

Potential and field   V2 − V1 = − ∫ E ⋅ dr 2

1

  ∂V ˆ ∂V ˆ ∂V ˆ E = −∇ V = − i− j− k ∂x ∂y ∂z

Rank the electric field magnitudes from largest to smallest.

Rules for field and equipotential lines • Electric field lines and equipotential lines are always perpendicular to each other • Equipotential lines NEVER cross • Electric field points in direction of decreasing potential • Denser equipotential lines (or electric field lines) => stronger electric field

Potential in a conductor A)Va>0 B)Va=0 C)Va0 B)Va=0 C)Va...