Electric Potential Introduction

4.1

Huh?Exam Date – Wed 2/9

Topics Covered Listed on Class WebsiteSample Exam from a few years back is also on the web.

TodayStart Unit 5: Electric Potential (Energy Methods)

Wednesday MondayMore of the same

Friday: Surprise – Quiz #2 (for real!)

YupSpring Break is just a few weeks away – (5ish)

Easy ClickThe figure shows the electric field lines in the vicinity of two point charges. Which one of the following statements concerning this situation is true?

A) q1 is negative and q2 is positive.B) The magnitude of the ratio (q2/ q1) is less than one.C) Both q1and q2 have the same sign of charge.D) The magnitude of the electric field is the same everywhere.E) The electric field is strongest midway between the charges.

A cubical Gaussian surface is placed in a uniform electric field as shown in the figure. The length of each edge of the cube is 1.0 m. The uniform electric field has a magnitude of 5.0 × 108 N/C and passes through the left and right sides of the cube perpendicular to the surface. What is the total electric flux leaving the cubical Gaussian surface?

A) 5.0 × 108 m2/CB) 3.0 × 109 N×m2/CC) 2.5 × 106 N×m2/CD) 1.5 × 107 N×m2/CE) zero N×m2/C

What is the electric flux passing leaving a Gaussian surface that surrounds a +0.075 C point charge?

A) 8.5 × 109 N×m2/CB) 6.8 × 108 N×m2/CC) 1.3 × 107 N×m2/CD) 4.9 × 106 N×m2/CE) 7.2 × 105 N×m2/C

e0= 8.85×10−12 SI Units

0

insideqe

A solid, conducting sphere of radius a carries an excess charge of +6 µC. This sphere is located at the center of a hollow, conducting sphere with an inner radius of b and an outer radius of c as shown. The hollow sphere also carries a total excess charge of +6 µC.

Determine the excess charge on the outer surface of the outer sphere (a distance c from the center of the system).A) zero coulombsB) –6 mCC) +6 mC D) +12 mCE) –12 mC

Recall

WHAT IS THE DEFINITIONOF WORK?????

+ Mrs. Field

Mr. External

3 Volunteers Please

Mrs. Field

Mr. External

E

+charge

Mr. ExternalMrs. Fields

That was

HARD WORK Mr. External

Sure WasMrs. Field

Each does the negative amount of work that the other one does.

ConstantSpeed

What did we do?

Remember:

The net work done by a conservative (field)force on a particle moving

around a closed path is

ZERO!

IMPORTANTThe work necessary for an external agent to move a charge from an initial point to a final point is INDEPENDENT OF THE PATH CHOSEN!

A few things to remember…A conservative force is NOT a Republican.An External Agent is NOT 007.

Start WORKING on Unit 5 Please