2 Electricity Test 4 Beiser Chapters 23-26 Multiple Choice Odd Supplementary Problems Every Other Odd (1not35not7) Browne Chapter 20-25 for PHY 222 20 313 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.2667 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.269270 8 Potential Difference
The amount of work needed to move a charge of 1C from one point to another.
Measured in volts (V)
Beiser p.266 9 Chap 23 - Summery 10 2368 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.2778 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.
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)
PowerShow.com is a leading presentation/slideshow sharing website. Whether your application is business, how-to, education, medicine, school, church, sales, marketing, online training or just for fun, PowerShow.com is a great resource. And, best of all, most of its cool features are free and easy to use.
You can use PowerShow.com to find and download example online PowerPoint ppt presentations on just about any topic you can imagine so you can learn how to improve your own slides and presentations for free. Or use it to find and download high-quality how-to PowerPoint ppt presentations with illustrated or animated slides that will teach you how to do something new, also for free. Or use it to upload your own PowerPoint slides so you can share them with your teachers, class, students, bosses, employees, customers, potential investors or the world. Or use it to create really cool photo slideshows - with 2D and 3D transitions, animation, and your choice of music - that you can share with your Facebook friends or Google+ circles. That's all free as well!
For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2D and 3D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on PowerShow.com are free to view, many are even free to download. (You can choose whether to allow people to download your original PowerPoint presentations and photo slideshows for a fee or free or not at all.) Check out PowerShow.com today - for FREE. There is truly something for everyone!