# Potential and Field - PowerPoint PPT Presentation

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Potential and Field. Connection between Potential and Fields Electric Field around a Conductor EMF or Batteries. Reading Questions. What quantity is represented by the symbol ?. 1. Electronic potential 2. Excitation potential 3. Electromotive force 4. Electric stopping power

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Potential and Field

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## Potential and Field

Connection between Potential and Fields

Electric Field around a Conductor

EMF or Batteries

What quantity is represented by the symbol ?

1. Electronic potential

2. Excitation potential

3. Electromotive force

4. Electric stopping power

5. Exosphericity

What quantity is represented by the symbol ?

1. Electronic potential

2. Excitation potential

3. Electromotive force

4. Electric stopping power

5. Exosphericity

The electric field

1. is always perpendicular to an equipotential surface.

2. is always tangent to an equipotential surface.

3. always bisects an equipotential surface.

4. makes an angle to an equipotential surface that depends on the amount of charge.

The electric field

1. is always perpendicular to an equipotential surface.

2. is always tangent to an equipotential surface.

3. always bisects an equipotential surface.

4. makes an angle to an equipotential surface that depends on the amount of charge.

The relationship ∆V=IR is called

2. Ampere’s law.

3. Ohm’s law.

4. Maxwell’s equation.

5. No name was given in this chapter.

The relationship ∆V=IR is called

2. Ampere’s law.

3. Ohm’s law.

4. Maxwell’s equation.

5. No name was given in this chapter.

Energy concept

### Electric Field and Potential

Force concept

Acts locally

Everywhere in space

Hand waving argument using a constant electric field

### Connecting Potential and Field

Recall from the last lecture we found

From Calculus III we find

Energy concept

### Electric Field and Potential

Force concept

Acts locally

Everywhere in space

• TACTICS BOX 30.1 ‑Finding the potential difference from the electric field

• 1)Draw a picture and identify the two points between which you wish to find the potential. Call them positions i and f.

• If you need to assign a specific value of V to a point in space, choose position f to be the zero point of the potential, usually at infinity.

• Establish a coordinate axis from i to f along which you already know or can easily determine the electric field component

• 4)Carry out the integral of Equation 30.3 to find the potential difference

### Potential from Electric Field

Calculating the potential from the electric field.

Or for one dimension

Recall

### Electric Field and Potential

Kirchhoff’s Loop Law

The sum of the voltages aroung a closed path equal zero.

### Student Workbook

You should do this one.

Vector

so

-

-

### Student Workbook

You should do this one.

### Class Question

Which potential-energy graph describes this electric field?

1. a

2. b

3. c

4. d

5. e

### Class Question

Which potential-energy graph describes this electric field?

1. a

2. b

3. c

4. d

5. e

Which set of equipotential surfaces matches this electric field?

(1)

(2)

(3)

(5)

(4)

### Class Question

Which set of equipotential surfaces matches this electric field?

(1)

(2)

(3)

(5)

(4)

Gaussian surface

+

+

### Class Question

Three charged, metal spheres of different radii are connected by a thin metal wire. The potential and electric field at the surface of each sphere are V and E. Which of the following is true?

1. V1 = V2 = V3 and E1 = E2 = E3

2. V1 = V2 = V3 and E1 > E2 > E3

3. V1 > V2 > V3 and E1 = E2 = E3

4. V1 > V2 > V3 and E1 > E2 > E3

5. V3 > V2 > V1 and E1 = E2 = E3

### Class Question

Three charged, metal spheres of different radii are connected by a thin metal wire. The potential and electric field at the surface of each sphere are V and E. Which of the following is true?

1. V1 = V2 = V3 and E1 = E2 = E3

2. V1 = V2 = V3 and E1 > E2 > E3

3. V1 > V2 > V3 and E1 = E2 = E3

4. V1 > V2 > V3 and E1 > E2 > E3

5. V3 > V2 > V1 and E1 = E2 = E3

### Student Workbook

You should do this one.

### Class Question

A wire connects the positive and negative terminals of a battery. Two identical wires connect the positive and negative terminals of an identical battery. Rank in order, from largest to smallest, the currents Ia to Id at points a to d.

1. Ia =Ib =Ic =Id

2. Ia =Ib >Ic =Id

3.Ic =Id >Ia =Ib

4. Ic =Id >Ia >Ib

5. Ia >Ib >Ic =Id

### Class Question

A wire connects the positive and negative terminals of a battery. Two identical wires connect the positive and negative terminals of an identical battery. Rank in order, from largest to smallest, the currents Ia to Id at points a to d.

1. Ia =Ib =Ic =Id

2. Ia =Ib >Ic =Id

3.Ic =Id >Ia =Ib

4. Ic =Id >Ia >Ib

5. Ia >Ib >Ic =Id