Engineering Physics Ii Set 1

Front 1

What is Electricity?

Back 1

The flow of electrons.

Front 2

Electric Charge

Back 2

Notations: Q or q

Comes in 2 types: positive (+) and negative (-) charge. 2 positive charges repel. 2 negative charges also repel. Opposites attract.

Front 3

Air is a _______?

Back 3

conductor

Front 4

Electric forces (are usually) _________ than gravity.

Back 4

stronger

Front 5

Conservation of Charge

Back 5

Charge can only be transferred. Energy, Momentum, Angular Momentum, and Kinetic Energy (in elastic collisions) are also conserved.

Front 6

Mass of an electron

Back 6

9.10938291 * 10^-31 kg

Front 7

Mass of a proton

Back 7

1.67262178 * 10^-27

Proton is about 2,000 times greater in mass than an electron.

Front 8

Electrons

Back 8

easily movable within an atom.

Front 9

Protons/Neutrons

Back 9

Found in the nucleus and are not easily movable. If moved definition of the object (material) changes.

Front 10

How can charges be transferred?

Back 10

Friction; rubbing 2 objects together can strip the electrons from one substance onto the other.

Induction; using a charged object to transfer charges without the 2 objects actually touching.

Front 11

Coulomb's Law

Back 11

where: r(hat) is just a vector direction and has no magnitude.

Front 12

Coulomb's Constant

Back 12

k(sub e) = 1/(4*pi*epsilon naught) = 8.987 * 10^9 (Nm^2)/C^2

Front 13

Coulomb

Back 13

The standard unit of measure of a charge.

Front 14

Charge of a proton/electron

Back 14

1.60217657 * 10^-19 C

protons are (+)

electrons are (-)

Front 15

Electric Field

Back 15

E(vector) = (kq)/r^2 r(hat)

F(vector) = qE(vector)

Front 16

lambda

Back 16

length/linear charge density = Q/L where: L = length.

SI units: Coulombs per meter (C/m)

Front 17

Sigma

Back 17

surface charge density = Q/A where: A = Area

SI units: Coulombs per square meter (C/m^2)

Front 18

rho

Back 18

volume charge density = Q/V where: V = volume

SI unit: Coulombs per cubic meter (C/m^3)

Front 19

Electric Field Integration

Back 19

E(vector) = integral(from a -> a+1) (k*lamda)/x^2 dx = ((kQ)/L) * (1/a - 1/(a+1)) = (kQ)/(a(a+1))

Front 20

Electric Flux

Back 20

the measure of flow of the electric field through a given area.

Front 21

Electric Flux

Back 21

the measure of flow of the electric field through a given area.

Front 22

Back 22

Integral for the entire enclosed surface

Front 23

Does shape matter with electric flux?

Back 23

No, what goes in will come out have a net of 0

Front 24

If there are no charges within a boundary then?

Back 24

The flux will always be 0

Front 25

Epsilon Not

Back 25

Know as the permittivity of free space. SI units of farads per meter (F/m) or coulombs squared per newton meter squared (C^2/N*m^2).

Front 26

Electrical Conductors

Back 26

Materials in which some of the electrons are free electrons that are not bound to atoms and can move relatively freely through the materials. All good conductors, once equilibrium is reached have a zero electric field inside.

Front 27

Electrical Insulators

Back 27

Materials in which all electrons are bound to atoms and cannot move freely through the materials.

Front 28

Semiconductors

Back 28

A third class of materials, and their electrical properties are somewhere between those of conductors and those of insulators.

Front 29

An electric field exist

Back 29

In the region of space around a charged object, the source charge.

Front 30

Electric field is defined

Back 30

As the electric force acting on a positive test charge (q) placed at that point divided by the test charge. E = F/q = -(deltaV)/d

A measure of rate of change of the electric potential with respect to the distance.

Front 31

SI units of Electric Field

Back 31

Newtons per coulomb (N/C) or Volt per meter (V/m)

Front 32

Gauss's Law

Back 32

Front 33

Electrostatic Equilibrium

Back 33

How ever much is coming in is going out. Balance within an object. Charges are done moving when electrostatic equilibrium is reached.

Front 34

Power and Work

Back 34

Front 35

Work (W)

Back 35

W = F(vector) (dot) ds(vector) where: ds(vector) is infinitesimal displacement vector.

W = qE(vector) (dot) ds(vector) = q(deltaV)

Front 36

Gauss's Law

Back 36

Front 37

Electric Potential (V) or simply the potential

Back 37

V = (deltaU)/q where: deltaU is the change in potential energy.

deltaV = - integrel E(vector) dot ds(vector) = -Ed

Front 38

SI units for electric potential

Back 38

Volt (V) => 1 V = 1 J/C (joules per coulomb)

Front 39

Work and Potential

Back 39

Front 40

Capacitance (Capacitor) (C)

Back 40

Stores electrical energy for later use. Two plates held apart, oppositely charged, creates (adds) electrical energy to the system for later use: C = Q/deltaV

Front 41

SI units for capacitance

Back 41

Farad (F) => 1 F = 1 C/V (coulomb per volt)

Commonly used in microFarads which is 10^-6

Front 42

Capacitance defenition

Back 42

The ratio of the magnitude of the charge on either conductor (plate) to the magnitude of the potential difference between them. Always positive (+). Electrical energy can be released all at once or a little at a time. Ex: defibrillator, flash in a camera.

Front 43

Capacitors in a series

Back 43

Front 44

Capacitors in parallel

Back 44

Front 45

Work in a capacitor

Back 45

W = Q^2 / 2C = 1/2 *Q*deltaV = 1/2 *deltaV^2*C

Front 46

Where is the energy being stored in a capacitor?

Back 46

In the electric field between the 2 plates.

Front 47

Energy Density (energy/volume)

Back 47

U / V = (1/2 *Epsilon Not *A * d * E^2) / (A * d) = (1/2) * Epsilon Not * E^2

Front 48

Dielectric

Back 48

Non-Conducting material placed inside the capacitor. Holds the plates apart, allowing a smaller distance between the plates. Lowering the potential difference between the plates, raising the capacitance.

deltaV = deltaV / k => C = Q / k = Q / (deltaV / k) = kC where: k is the dielectric constant of the material used.

Front 49

Dielectric Strength

Back 49

Equals the max electric field that can exist in a dielectric without electrical breakdown. Note: the values depend strongly on the presence of impurities and flaws in the material.

Front 50

Change in potential or potential difference

Back 50

deltaV: exists solely because of a source charge and depends on the source charge distribution. Must have 2 or more charges to exist.

Front 51

Electron Volt (eV)

Back 51

1 eV = 1.6 * 10^-19 C (V) = 1.6 * 10^-19 J

Front 52

Which direction do electric field lines point?

Back 52

In the direction of decreasing electric potential

Front 53

Calculating Capacitance

Back 53

C = Q / deltaV = Q / (kQ/r) = r / k

= 4 * pi *Epsilon Not * r where: r = radius

Front 54

Electric Dipole

Back 54

Front 55

Electric Dipole Moment

Back 55

p = 2 * a * q where: 2 * a is the distance between the charges q and -q. Direction vector is from the negative charge toward the positive charge.

Front 56

Charge of a capacitor time constant

Back 56

After 5 time constants a capacitor is considered to be 99% charged.

Front 57

torque = p(vector) x(cross product) E(vector)

Back 57

Torque acting on an electric dipole in a uniform electric field E.

Front 58

U = -p(vector) dot E(vector)

Back 58

The potential energy (U) of the system of an electric dipole in uniform external electric field E.