ELECTRIC EEL CRITC

of, or relating to, electricity

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FIELDDI ELFa region of space characterized by a physical property

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POTENTIALLET IN A POT

capable of being but not yet in existence

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POTENTIAL DIFFERENCEA CENTRED FINE PET FOILthe amount of energy per unit charge needed to move a charged particle from a reference point to a designated point in a static electric field

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CAPACITANCEAN ACETIC CAPthe ratio of charge to potential on an electrically charged, isolated conductor

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POTENTIAL ENERGYA TEETERING PYLON

the mechanical energy that a body has by virtue of its position or location in a force field

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Terms to Remember:• ELECTRIC FIELD

• ELECTRIC POTENTIAL ENERGY

• ELECTRIC POTENTIAL

• POTENTIAL DIFFERENCE / VOLTAGE

• CAPACITANCE

• CURRENT

Electric Field – the property of space around a charged object that causes forces on other charged objects.

The field lines originate from the positive charge.

The field lines end up at the negative charge.

Electric fields can be drawn using field lines. They are also called force lines.

A positive charge exerts out, and a negative charge exerts in, equally in all directions.

Electric Field Intensity is defined as the electric force per unit charge.

The direction of the field is taken to be the direction of the force it would exert on a positive test charge.

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VAN DE GRAAFF GENERATOR

Robert Van de Graaf devised the high-voltage electrostatics generator.

A Van de Graaf’s generator is a device that transfers large amounts of charge

When a person touches a Van de Graaf’s generator, the results can be dramatic.

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In the Van de Graaf generator charge is transferred onto moving belt and from the belt to the metal dome. An electric motor does the work to increase the electric potentialEnergy.

VAN DE GRAAFF GENERATOR

In equation form,

where:

E – electric field strength

F – electrical force

q – magnitude of the charge

In SI units,

F – newtons ( N)

q – coulombs (C)

E – newton/coulomb (N/C)

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Electric Field of Point Charge

The electric field of a point charge can be obtained from Coulomb’s Law:

                                        

 

Electric field between two oppositely-charged parallel plates

e-

Wdone = Egained

W = Fd

EPE = Fd

EPE = Eqd

where Egained = electric potential energy

EPE = Eqd

where:

E – electric field strength

q – magnitude of the charge

d – distance

EPE – electric potential energy

In SI units,

E – newton/coulomb (N/C)

q – coulombs (C)

d – meters (m)

EPE – joules (J)

But a more useful concept is the electric potential energy of each charge

e-

e-

e-

e-

The greater the magnitude of the charge, the greater is the electric potential energy

Electric Potential - potential energy per unit charge

where:

EPE – electric potential energy

q – magnitude of the charge

V – electric potential

In SI units,

EPE – joules (J)

q – coulombs (C)

V – joule/coulomb (J/C)

- volt (V)

V = Edwhere:

E – electric field strength

d - distance

V – electric potential

In SI units,

E – newton/coulomb (N/C)

d – meters (m)

V – newton-meter/coulomb

- joule/coulomb (J/C)

- volt (V)

NB: V is a function of d

e-

A B

W = 120 J

q = 1 C

EPE = 120 J

V = EPE/q

Va = 0

Vb = 120 J/ 1C

= 120 V

Potential Difference – difference in potential between any two points in an electric field

Vab = Vb – Va

- also known as voltage

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V = W / q

Electric Potential Difference

Electric potential difference or voltage is the change in potential energy per unit charge in an electric field.

Volts = joules/ coulomb

The concept of “potential difference" or “voltage" in electricity is similar to the concept of "height" in gravity, or “pressure” in fluids

Charges will move from an area of higher potential to an area of lower potential

e-

e- e- e-e-e-

…and when charges move in a conductor, CURRENT is established

e- e- e-e-e-e- e- e-e-e-e- e- e-\e-e-e-e- e- e- e-e- e-e-

where:

q – magnitude of the charge

t - time

I – current

In SI units,

q –coulomb (C)

t – seconds (s)

I – coulomb/second (C/s)

- ampere (A)

Is there a way to store electric potential energy?

Capacitors

Capacitor – is made up of two oppositely charged parallel plates with vacuum or an insulator between them

- stores charge

- because work is done to add charges, the capacitor also stores electric potential energy

Capacitance – is a measure of the capacitor’s ability to store electric energy

- is equal to the ratio of the magnitude of the charges stored to the potential difference between the plates.

where:

q – magnitude of the charge

V – potential/potential difference

C - capacitance

In SI units,

q – coulomb (C)

V – volt (V)

C – coulomb/volt

- farad (F)

Complete the table.Complete the table.

QuantityQuantity Definition/ Definition/ EquationEquation

SI UnitSI Unit

Electric FieldElectric Field EE = F/q = F/q N/CN/C

Electric Potential EnergyElectric Potential Energy EPE = EPE = EEqdqd JJ

Electric PotentialElectric Potential V = EPE/q or V = EPE/q or V=V=EEdd

J/C or VJ/C or V

Potential DifferencePotential Difference VVab ab = V= Vbb - V - Vaa VV

CapacitanceCapacitance CC = q/V = q/V C/V or FC/V or F

CurrentCurrent I = q/tI = q/t C/s or AC/s or A

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