Physics II PHY 202222 Electricity - PowerPoint PPT Presentation

1 / 72
About This Presentation
Title:

Physics II PHY 202222 Electricity

Description:

Resistor a material through which current flows with some difficulty ... Resistors in Series. Current 'has to fight it's way through' R1 then R2 and then R3 ... – PowerPoint PPT presentation

Number of Views:78
Avg rating:3.0/5.0
Slides: 73
Provided by: lcr7
Category:

less

Transcript and Presenter's Notes

Title: Physics II PHY 202222 Electricity


1
Physics II PHY 202/222 Electricity
  • 452 South Anderson Road
  • Rock Hill, SC 29730
  • www.yorktech.com

2
Electricity Test 4
Beiser Chapters 23-26 Multiple Choice
Odd Supplementary Problems Every Other Odd
(1,not3,5,not7) Browne Chapter 20-25 for PHY
222 20 3,13 21 8 22 5 24 7 25 9
3
Chapter 23 Electricity
Beiser p.266
4
Electric Charge
  • Positive charge from protons
  • Negative charge from electrons
  • Measured in Coulombs (C)
  • e 1.6 x 10-19 C

Like charges repel. Unlike charges attract.
_
_
_



Coulombs Law
Beiser p.266
5
Coulombs Law Example
_

Find the force of attraction between a ball with
a charge of 0.2 C and a ball with a charge of
-0.3 C if they are separated by .5 m.
Beiser p.266,7
6
Superposition of Electric Forces
  • Find the electric force on Q3 from the other
    charges.

Fnet
350
Beiser p.269
7
Electric Fields
If you had a small positive test charge and
placed it near other charges, it would experience
a force at every point in space. Mapping these
lines of force show the electric field. Measured
in N/C or V/m.
Beiser p.269,270
8
Potential Difference
  • The amount of work needed to move a charge of 1C
    from one point to another.
  • Measured in volts (V)
  • 1V 1J/C

Beiser p.266
9
Chap 23 - Summery
10
236,8
11
23.10
12
23.12
q2
q
x
40 - x
40 cm
13
23.14
14
23.16
100 V
15
23.18
- - - -

F
16
23.20
17
Chapter 24 Electric Current
Beiser p.277
18
Current
  • The flow of charge
  • Measured in Amperes (or Amps), A
  • 1 A 1 C/s

Beiser p.277,8
19
Direction of Current
  • A complete circuit is needed for electrons to
    travel.
  • Electrons actually travel from negative terminal
    of battery to positive.
  • Current is said to go from positive to negative.

Direction of current is positive to negative

V 12 V
Mr. Electron sez Im going this way!
20
Conductors Insulators
  • Conductors a material through which current
    flows easily
  • Insulator - a material through which current will
    not (generally) flow
  • Resistor a material through which current flows
    with some difficulty
  • Semiconductor - a material that is sometimes a
    conductor sometimes a resistor
  • Superconductor a material that carries current
    effortlessly with no loss

Beiser p.277
21
Resistance
  • A measure of the opposition to current in a given
    material
  • Measured in Ohms (O)
  • 1 O 1 V/A
  • A resistor is a device with resistance

Resistor color band example red yellow blue is 2
4 6 so 24x106O
R 24x106 O
Beiser p.278
22
Ohms Law
  • Relates current, voltage and resistance.
  • It takes more voltage to push current through a
    high resistance material

Beiser p.278
23
Power
  • The rate at which work is done to maintain
    current.
  • or
  • The rate at which a current at a voltage can do
    work
  • Measured in Watts (W)
  • 1 W 1 J/s

Beiser p.282
24
24.2
25
24.4
26
24.6
27
24.8
28
24.10
29
24.12
30
24.14
31
24.16
32
24.18
33
24.20
34
Chapter 25 Direct Current Circuits
Beiser p.288
35
Resistors in Series
  • Current has to fight its way through R1 then
    R2 and then R3
  • Add resistors in series.
  • RTotal R1, R2 R3 100 O 300 O 500 O
    900 O

Beiser p.288
36
Resistors in Parallel
  • Current can choose to go through R1 or R2, so
    total resistance is less that either individual
    resistor.
  • Use formula to get total resistance

TI-83 keystrokes
Mr. Electron sez Whee! I can go either way.
That makes it easy for me/hard for you!
Beiser p.290
37
Combinations of Resistors
Mr. Electron sez looks like fun!
1) Add the parallel resistors
2) Add the series resistors
RTotal 191 O
3) Add the parallel resistors
Beiser p.293
38
EMF Internal Resistance
  • Batteries have a small internal resistance so
    that
  • V Ve Ir or
  • Terminal Voltage emf potential drop due to
    internal resistance
  • The total internal resistance of batteries in
    series is the sum of the individual internal
    resistances.
  • The total voltage of batteries in series is the
    sum of the individual batteries.

Beiser p.294
39
Batteries in Series
  • The total voltage of batteries in series is the
    sum of the individual batteries.
  • The total internal resistance is the sum of the
    individual internal resistances

Beiser p.295
40
Batteries in Parallel
  • Batteries in parallel should always have the same
    voltage, so that back currents dont flow through
    the weaker batteries and waste power.
  • The total voltage of batteries in parallel is the
    voltage of any of the batteries.
  • The total internal resistance is added like
    resistors in parallel.

Beiser p.295
41
Kirchhoffs Rules
  • The sum of the currents into any point is equal
    to the sum of the current from that point,
  • The sum of the voltage around a loop is zero.

Beiser p.298
42
Kirchhoff Example 1
  • Step 1 pick a point where all the legs of the
    circuit come together.
  • Step 2 pick a direction that you think current
    will flow in each leg and label each leg as I1,
    I2
  • Step 3 The current into point A the current
    out of point A I1 I2 I3
  • Step 4 Trace a complete circuit and add the
    voltages batteries increase and resistors
    decrease see 4 12V I1R1 I2R2 0 (If
    moving against the current reverse the signs)
  • Step 5 Trace another path see 5 12V
    I1R1 I3R3 0
  • Solve the three simultaneous equations

Beiser p.299-302
43
Solving by Substitution Method
Substitute both into eq.1
I1 I2 I3 12 I1R1 I2R2 0 12 I1R1 I3R3 0
Solve eq.2 for I2, and eq.3 for I3.
Substitute into eq.2 and eq.3
44
Solving by matrices
On TI-83
45
25.2
46
25.4
47
25.6
48
25.8
49
25.10
50
25.12
51
25.14
52
25.16
53
25.18
54
Example 25.21
55
25.22
56
25.24
57
Chapter 26 Capacitance
Beiser p.308
58
Capacitors Capacitance
  • A capacitor is a device that stores charge.

A voltage can push electrons around to store
charge on a capacitor. Capacitance is the ratio
of charge to voltage.
Capacitance is measured in farads.
Beiser p.308
59
Capacitors in Parallel
Beiser p.310
60
Capacitors in Series
If C1 100 F and C2 300 F TI-83 keystrokes
Beiser p.310
61
Energy of a Capacitor
When charge is stored in a capacitor, the amount
of stored or potential energy is given by any of
the following
Beiser p.312
62
Capacitor Charging
  • For a capacitor that initially has no charge,
    these three formulas govern capacitor charging
    when the switch is closed
  • The first gives current or rate of charging at
    any time
  • The second is the TIME CONSTANT a which tells
    how long it takes to charge a capacitor to 63 of
    its capacity.
  • The last gives the amount of charge at any time.

Beiser p.313
63
Capacitor Discharging
  • For a capacitor that initially is fully charged,
    when the switch is closed
  • The first is the TIME CONSTANT a which tells
    how long it takes to discharge 63 of the full
    charge of the capacitor (or how long it takes to
    fall to 37 of capacity)
  • The last gives the amount of charge at any time.

Beiser p.314
Beiser p.313
64
26.2
65
26.4
66
26.6
67
26.8
68
26.10
69
26.12
70
26.14
71
26.16
72
26.18
Write a Comment
User Comments (0)
About PowerShow.com