electricity Flashcards
(80 cards)
1
Q
Simple circuit
A
- wires
- power supply
- power user
2
Q
Electricity
A
Moving e-
3
Q
Resistance
A
Prevents e- flow
4
Q
Resistance R unit?
A
Ω ohms
5
Q
Electromotive force emf
A
Energy added by batteries
6
Q
Emf (fancy E) unit?
A
- V (voltage)
- only batteries
7
Q
Potential difference
A
- voltage
- measure of energy change
8
Q
Potential difference (voltage) V unit?
A
Unit V (volts)
9
Q
Current
Current intensity
A
How many e- are flowing
10
Q
Electric current I unit?
A
A (ampers)
11
Q
Voltmeter
A
Draw
12
Q
Charge
A
Total # of e- stored/, used
Q
13
Q
Electric charge Q unit?
A
A-h or C
14
Q
Time t unit
A
Hr or sec
15
Q
V=IR
A
Ohms law
16
Q
Ammeter
A
Draw
17
Q
Conductors
A
Allows e- to flow
-copper, neutral aluminum
18
Q
Resistive conductors
A
Allow e-to for but creates heat
-nichrome, tungsten
19
Q
Insulators
A
Do not let e-flow (prevent e- flow)
-plastic, glass
20
Q
Semi-conductors
A
Sometimes let e-flow
- used in electronics
- germanium, silicon
21
Q
How the resistance of an object is calculated
A
Write
22
Q
Resistivity
A
- inherent property
- unit ohm/m
23
Q
Series
A
- all in a row, one after another
- no choice! All current in one component has to go into the other
Emf=V1+V2+V3…
Req=R1+R2+R3…
It=I1=I2=I3=….
24
Q
Series equations
A
Emf=V1+V2+V3…
Req=R1+R2+R3…
It=I1=I2=I3=….
25
Parallel
- branch circuits
| - has no choice! Needs to choose a part. Current has a choice between components
26
Series equations
V=V2=V3
It=I1+I2+I3
1/Req=1/R1+1/R2+1/R3...
1/Req=1/2+1/3 Req =6/5
1/Req=3/6+2/6=5/6
27
Steps in analyzing a circuit
1. Find Req
2. Find It or Emf
3. Find rest of missing values
28
Req series...
Req=R1+R2+R3...
29
Series current
I stays the same
30
Series voltage law
V is additive
| Vt=V1+V2+V3...
31
Battery in series
Add up all V's
32
Parallel Req
1/Req=1/R1+1/R2+1/R3
33
Parallel (current law)
It=I1+I2+I3...
34
Batteries parallel
Last longer
35
DC
- Direct current
- powered by batteries
- V and I do not change
- draw
36
AC
- alternating current
- V and I oscillate
- draw
- how fast it changes is measured in hertz Hz
37
Transformer
Change Voltage
38
Rectifier
AC to DC
39
Inverters
DC to AC
40
Residential circuits (in houses)
Composed of red, black (=live 120V), and white (=0V neutral)
41
Black wire
120V
42
Red write
120V
43
White wire
0V
44
120V hook up
120V (black or red)
0V (white)
Ground (bare copper)
45
240V hook up
2- 120V (red and black)
0V (white)
Ground (bare copper)
46
Universal/general branch circuit
- lights, plugs (receptacle)
| - 120V
47
Single/dedicated branch circuit
- 1 large appliance
| - -240V
48
240V appliances
- 120V light usage
- 240V heavy usage
- can pull either
49
Transmission lines
High voltage (10KV+) leads to reduced power lost
50
Distribution network (10KV down)
-delivery to houses and individual buildings
51
Step-up transformers
-Increase the Voltage
-Decrease current
going in P=V1I1
P2=V2comingoutV2
52
Step-down transformers
- Decease Voltage
| - Increase current
53
Dry hand
High resistance V=IR
54
Wet hand
Low resistanc
55
Electric shocks
- Complete a circuit
| - Touch a source and a drain (ground)
56
3 prong plugs
- metal appliances
| - grounds the housing (outside) to prevent shocks
57
Charges on a conductor
Draw
| Evenly spread out
58
Charges on an insulator
draw
| stay where placed
59
Electrification by friction
- Rub two items together
- one becomes +
- one becomes -
60
Electrification by contact
Charged object gives some of it`s charge to neutral item
61
Electrification by induction
charged object pushes away like charges, creates a local opposite charge
62
Van de graff
- Is positively charged
- Electrifies person by contact
- all charge is positive, so like charges repel
63
Humidity
allows charge to dissipate
64
Sparks
electricity jumping on air gap
65
Solution to 99% of problems from static electricity
Grounding
66
Electrostatic paint guns
- Electrify object
- Paint has opposite charge
- opposites attract
67
Plastic wrap
- Wrap has a charge
- wrap induces a charge on the bowl
- charges are opposite, so they attract
68
How does electrostatics work
- electrification of first object
- electrification of second object
- charges - same repel --- different attract
69
What happens when you cut a magnet
get two smaller magnets
70
Magnetic fields
exit at north
| enter at south
71
Electromagnets
Coils of wire with electricity flowing through them
72
Magnetic induction
Generate (create) current using magnets and movement
or
Create movement using currents and magnets
73
Generators
Movement --into-- electricity
74
Motor
electricity --into-- movement
75
Rotors
Rotate, pieces that rotate
76
Stators
Stay still, pieces that stay still
77
Motors-generators increase Voltage
Increase speed-rotation
78
Motors-generators increase number of turns
more power
79
Proportional
- Both variable do the same thing
- Opposite side and same level of fraction
- Same side and opposite level
80
Inversely proportional
- Variables do opposite
- same side and same level
- opposite side and opposite level
