Electric Fields

What is an Electric Field?

Answer Me!!!

Explain what you think this drawing means? What is the significance of the arrows?

Electric Field

Any place where an electrostatic force exists, there is an electric field.

Electric field strength is determined by the following formula:

couloumbs)(in charge

force ticelectrostastrength field Electric

q

FE e

Practice Problem 1

An electrostatic force of 20 N is exerted on a charge of 8.0x10-2 C at point P in an electric field. What is the magnitude of the electric field intensity at P?

Practice Problem 2

At point P in an electric field, the magnitude of the electrostatic force on a proton is 4.0 x 10-10 N. What is the magnitude of the electric field intensity at point P?

Practice Problem 3

Draw the graph that best represents the relationship between electric field intensity and distance from a point charge.

Distance

Ele

ctric

Fie

ldIn

tens

ity

Final Thought…

What is the magnitude of the electrostatic force experienced by one elementary charge at a point in an electric field where the electric field intensity is 3.0 x 103 N/C?

Answer Me!!!

Draw a diagram that represents the electric field around a negatively charged conducting sphere.

-

Electric Fields around Point Charges and Spheres Electric Field Lines show where an electric

field is. The closer together the lines are, the stronger the electric field

+ -

Electric Field Lines go away from positive charges. Lines are perpendicular to the sphere

Electric Field Lines go towardnegative charges. Lines are perpendicular to the sphere

Electric Field Lines with Multiple Charges

Electric field lines go away from positive and toward negative charge. Electric field lines never intersect.

+ -

Electric Field Lines

Field lines between two positively charged particles go away from each other.

Field lines between two negatively charged particles go away from each other.

+ + - -

Practice Problem 6

A positive test charge is placed between an electron e and a proton p. Which way will the test charge move?

e- p+

+

Practice Problem 7

An object with a net charge of 4.80 x 10-6 C experiences an electrostatic force having a magnitude of 6.00 x 10-2 N when placed near a negatively charged metal sphere. What is the electric field strength at this location?

Electric Field Lines Between Two Plates

Electric field lines go away from a positive plate and go toward the negative plate. Electric field strength is the same everywhere between the plates.

Positive Plate (+)

Negative Plate (-)

+Accelerates toward negative plate -

Accelerates toward positive plate

Practice Problem 8

The diagram represents a source of potential difference connected to two large, parallel metal plates separated by a distance of 4.0 x 10-3 m. Which statement describes the electric field strength between the plates? It is zero at point B It is maximum at point B It is maximum at point C It is the same at points

A, B and C

Potential Source

+++++++

- - - - - - -

AB

C

Practice Problem 9

If an electron is introduced directly between two oppositely charged, parallel plates, the electron will Travel at constant speed toward the positively

charged plate. Travel at constant speed toward the negatively

charged plate. Accelerate toward the positively charged plate. Accelerate toward the negatively charged plate.

Final Thought…

A proton, neutron and electron are located between two oppositely charged plates, the magnitude of acceleration will be greatest for the Proton Neutron electron

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

p+

ne-

Answer Me!!!

What is the difference in potential energy between a 2 kg ball 10 meters in the air compared to a 2 kg ball 2 meters in the air?

Potential Differences

Opposite charges attract. Same charges repel. The potential difference between two points in an

electric field is the work required per unit charge to move between the points.

Potential difference is given by the formula:

Coulombs)(in charge

Joules)(in Work difference Potential

q

WV

Potential Difference

If 1 Joule of work is done to move 1 Coulomb of charge between two points, a potential difference of 1 volt is said to exist.1 J/C = 1 V

If an elementary particle is moved against an electric field through a potential difference of 1 volt, the work done is 1 electronvolt.1eV = (1.00 V)*(1.6x10-19 C) =1.6x10-19 J

Practice Problem 11

The units volts/meter measure the same quantity asJoules/voltNewtons/ampere*meterNewton*meters2/coulomb2

Newtons/Coulomb

Practice Problem 12

Moving 2.5 x 10-6 C of charge from point A to point B in an electric field requires 6.3 x 10-4 J of work. What is the potential difference between points A and B?

Practice Problem 13

If 4.8 x 10-17 J of work is required to move an electron between two points in an electric field, what is the electric potential difference between these points?

Practice Problem 14

How much work is required to move a single electron through a potential difference of 100 V?

Practice Problem 15

What is the energy required to move one elementary charge through a potential difference of 5 V?

Final Thought…

How many electronvolts are in one Joule?