Electricity

Question 1

Electric field (E)

Answer 1

E = electrostatic force per unit charge

Strength of field at any point = potential

Analogous to gravity

Question 2

Voltage (V)

Answer 2

V = energy per unit charge

V = potential for work by an electric field in moving any charge from one point to another

V = Ed

Analagous to gh

Difference b/w cathode and anode

Question 3

Electric force

Answer 3

Attractive or repulsive

Exists b/w any two charges

Inversely proportional to square of distance b/w them

Acts through fields that exert given force per unit charge

Question 4

Gravitational force

Answer 4

Always attractive

Exists b/w any two masses

Acts through fields that exert force per unit mass

Question 5

Charges move from _____ to _____

Answer 5

Higher potential to lower potential (current)

Cathode to anode

Question 6

Charge

Answer 6

Part of identity of subatomic partcles

Question 7

Current runs in ____

Answer 7

Opposite direction of electrons

Question 8

Units of charge (q)

Answer 8

Coulombs (C)

Question 9

Coulomb’s Law

Answer 9

F = k((q1∗q2)/r^2 )

```
k = Coulomb’s constant
(r = distance b/w centers of charge)
~~~

Question 10

Universal Law of Conservation of Charge

Answer 10

Universe has no net charge

Question 11

Charge is quantized

Answer 11

Any charge must be at least as large as smallest possible unit

Question 12

Similarities b/w gravity and electricity

Answer 12

Both mass and charge create fields

Both change inversely w/ square of distance b/w two centers

Question 13

Field

Answer 13

Distortion of condition in space that creates force on charge/mass

Represented by lines of force

Question 14

Lines of force

Answer 14

Point in direction of field (positive to negative for electric fields, towards mass for gravity)

Distance b/w lines = strength of fields
(Closer = stronger field)

Never intersect

Question 15

Units of E

Answer 15

N/C or V/m

Question 16

Force on a charge in an electric field

Answer 16

F = qE

Question 17

Center of charge

Answer 17

Point from which charge is generated

Question 18

Potential energy of charge in electric field

Answer 18

U = qEd

d = displacement

Question 19

Units of voltage

Answer 19

Volts (V)

J/C

Question 20

Conductors

Answer 20

Allow electrons to flow freely

Ex. metals

Question 21

Resistors

Answer 21

Hold electrons in place

Ex. diamond, glass

Question 22

Current

Answer 22

Moving charge

Moves in opposite direction of electron flow (higher potential to lower potential = cathode to anode)

Question 23

Units of current

Answer 23

Amps (A)

C/s

Question 24

Cathode

Answer 24

Higher potential

Question 25

Anode

Answer 25

Lower potential

Question 26

Current flows from…

Answer 26

Cathode (high potential) to anode (low potential)

Question 27

Electrons flow from…

Answer 27

Anode (low potential) to cathode (high potential)

Question 28

Circuit

Answer 28

Cyclical pathway for moving charge

Question 29

Resistivity

Answer 29

Measure of substances resisting flow of charge (rho)

Question 30

Resistance (R)

Answer 30

Measure of object of particular size/shape to resist flow of charge

R = pL/A

Question 31

Units of resistance

Answer 31

ohms (omega)

Question 32

Ohm’s Law

Answer 32

I = V/R

Question 33

Battery

Answer 33

Adds energy to circuit

Pumps ‘fluid’ to greater height

Rated by electromotive force (EMF) = voltage

Question 34

Capacitor

Answer 34

Temporarily stores energy in a circuit in form of separated charge

C = kAe/d
(A = plate area)
(d = separation distance)
(k = dielectric constant = substance b/w plates)

Stores energy for quick use in future

Question 35

Parallel plate capacitor

Answer 35

Two plates made form conductive material separated by a small distance

Question 36

Capacitance

Answer 36

Ability to store charge per unit volume

High capacity = store a lot of charge at low voltage

Question 37

Formula for capacitance

Answer 37

C = Q/V

Question 38

U = …

Answer 38

U = 1/2 QV

Question 39

Dielectric constant

Answer 39

Must be insulator to build up charge

Resists creation of electric fields => allows capacitor to have greater capacitance (store more charge)

Randomly oriented dipoles

Question 40

Series

Answer 40

Two components not separated by a node

Components line up in a row

Question 41

Resistors in series

Answer 41

R(effective) = R1 + R2 +…

Thought of as single resistor with length with sum of length of individual resistors

Increasing length => increases resistance

Question 42

Parallel

Answer 42

Single components in alternate paths connecting same nodes

Question 43

Resistors in parallel

Answer 43

1/R(eff) = 1/R1 + 1/R2 +…

Single resistor w/ cross-sectional area that is the sum of cross-sectional areas of resistors in parallel

Increase cross-sectional area => decrease resistance

Question 44

Resistors = toll booths

Answer 44

Series: three toll booths = one big toll both (slow)

Parallel: traffic can pass through one of three booths in parallel (fast)

Question 45

Capacitors in parallel

Answer 45

C(eff) = C1 + C2 +…

Single capacitor w/ plate area that equals sum of areas of capacitors in parallel

Increase area => increase capacitance

Question 46

Capacitors in series

Answer 46

1/C(eff) = 1/C1 + 1/C2 +…

Single capacitor w/ distance b/w plates that is the distance b/w first plate of first capacitor and last plate of last capacitor

Question 47

Magnetic field

Answer 47

Created by magnet

Concurrent w/ electric field

Represented by lines of force (from north to south)

Question 48

Units of magnetic field

Answer 48

Strength measured in tesla (T)

Question 49

What produces magnetic fields?

Answer 49

Only moving charges

All charges, static and moving, produce electric field

Question 50

Charge through magnetic field experiences what forces?

Answer 50

Force perpendicular to both velocity and magnetic field

Question 51

Units of electric field

Answer 51

Volts/meter