Wright State University Lake Campus/2017-9/Phy2410/log

Before Test 3

T 29 August 2017 (UTC)

Sorry! I lectured from last year's study guide. The echo and sound wave questions are not on this exam. Use the new study guide.

Lecture: Study guide. Attendance policy.

Lab: Mr Circuit inventory

Do not come on Tuesday unless you are in that section. But if you are in the Tuesday section you are more than welcome to switch to Thursday. We will discuss attendance and how lab reports will be done. First lab: Inventory Mr. Circuit and

R 31 August T1 study guide

1/4 from 1381800 to c07energy_lineIntegral
2/4 from 1378605 to a18ElectricChargeField_findE

see above

T 5 September 2017 Find E from 2 point sources

Lecture: Defined electric field, field point, source point, coulomb, amp. Did coulomb's law for first quiz (find E). Discussed the vector addition problem, using the unit vector as the r vector divided by its amplitude. Showed them the hard problem (dipole) but did not solve in class/

Lab

Work in groups of five or less and to the sparkfun website and find a topic, explain it, and pose a multiple choice question on it. All reports must be handed in on paper, but a permalink to your WV userpage is good enough. I can find you a place to write if you have no place on Wikiversity. As an alternative you can also do the hydraulic analogy to current, voltage, resistor, node and/or capacitor.

Th 7 September 2017 Line integral to find E field (also Tue 12 Sep)

Analyse a breadboard circuit found on commons:main page

1. Draw circuit schematic
2. Make the circuit
3. Measure the voltage accross:
1. LED 1.81V
2. resister 5.58V
3. Battery 7.44V
Two add to the third. Calculate discrepency and %error.

How not to abuse a voltmeter

• Never measure resistance of anything that is connected to a circuit.
• Explanation: Begin with the "resistance" measurement of an LED, and note how it might glow.
• Equivalent circuit of a voltmeter.

Make it possible for a person to read your report and know what you did: We constructed this circuit after looking at a photograph depicting a breadboard connected to four 1.5 volt batteries.

T 12 Sep

• How many need batteries?
• How many can attend the recitation (even if you don't want to)?
• Do not panic: The following is needed to get an A, but probably not a B. It will help if you make an effort to learn it because we do a simpler version of it later: 3/13 from 1390982 to c18ElectricChargeField_lineCharges -- (text: V2 Ch. 5)*solutions This is how the study guide looks now.

Planned Lecture: Equations#19-Electric_Potential_and_Electric_Field F=qE ... E=kq/r2 ... ΔV=Edcosθ, where F is force (Newtons), q is charge (Coulombs), V is "Electric Potential" (or simply "Volts"), r is distance. Note this gives you two equivalent units for E: N/C (newtons/coulomb) and V/m (volts/meter). The only other thing you need to know by heart is that 1 A = 1 C/s (amp is a coulomb per second, or the rate at which charge flows through a wire).

Later we do the capacity of an object to store charge at a given voltage: Q=CV, where C is the capacitance. A large parallel plate capacitor has a large area with the plates close together (which keeps the voltage down).

Before T1: shorter equation sheet

See File:Guy vandegrift pdf.pdf, which is best read online by clicking "original file" or going straight to it at https://upload.wikimedia.org/wikiversity/en/d/d5/Guy_vandegrift_pdf.pdf

Do A6 (How a diode works) on page 20-21, and note how this "one-way" street works differently in each direction.

Here, you will try to understand in more depth why the diode fails to operate when "backwards". Do this by measuring the voltage at each point (with respect to the negative side of the battery which we shall call "ground" (zero volts).

Do A7 (SCR) and note how it acts as an electronically activated switch

I don't even know what is going on here. We will find out.

Tues 26 September-Just like Thursdaʏ

Lab report templatesː official .. informal handwritten

Thur 28 sept

Lecture: We covered all of Test 2 except the last two Gauss law problems and the power drift velocity quiz.

Malus Law lab

Into: Malus's law predicts how much light comes out of a polarizing filter if the incident light is already polarized.

• Bell's theorem
• Relates electric field to light's intensity. (Watts per square meter)
• Excuse to explore error analysis based hand-drawn sketch.

Procedure: Carefully draw an equilatoral triangle and bisect it with a perpendicular to a midpoint. Divide the long side into 10 parts by first cutting it in half, and making a 2/3 split before cutting it into five equal pieces. Estimate the height of the triangle.

• Do the math. Were you correct to within experimental error.
• Given:
Power of light passing a window is proportional to the square of the electric field. Use this to "calculate" the probability of a photon passing a filter held 30 degrees to the photon's polarization. Hint: If the beam's power is cut in half, the probability must be 50%.
• Bell' thm: If Alice passes a fiter at 0 degrees (i.e. ) then Bob would also pass at that angle. But if Bob sees a different angle (e.g. ♣ or ♠), what is his probability of passing? Hint: They would break even in the solitaire game.

Mr. Circuit

Lab kit A8 page 24 npn transistor.

Tues 17 Oct

How many Thursday Lab people say "yes" to these three quesitions:

1. I cannot attend the lab today from 3:30-5:30 (instead of Thursday).
2. I cannot attend the recisitation at 5:30 today.
3. XXX

prep for T3 24 October

• Test 3 is Thursday November 16, 2017

The first listed quiz is a repeat of line integrals. Only one out of 13 questions will be on this quiz.

Thurs 26 October Magnetic fields, cross product and right hand rules

Lab:Nine volt batteries in series

Wikipedia gives the following values for the total body impedance of a hand to hand circuit for dry skin, large contact areas, 50 Hz AC currents (the columns contain the distribution of the impedance in the population percentile; for example at 100 V 50% of the population had an impedance of 1875Ω or less):[1]

Voltage 5% 50% 95%
25 V 1,750 Ω 3,250 Ω 6,100 Ω
100 V 1,200 Ω 1,875 Ω 3,200 Ω
220 V 1,000 Ω 1,350 Ω 2,125 Ω
1000 V 700 Ω 1,050 Ω 1,500 Ω

Another source quotes 500Ω as the resistance of the body, with a skin resistance of 1500Ω.[2] We have alkaline 9V batteries with an internal impedance expected to be 1-2Ω[3]

data

One 9V battery with a 10W 20-Ohm resistor. Measured voltage was 7.42 volts. Open terminal voltage was 9.26V. Internal resistance is 5.1 ohms.

Repeat with same resistor different battery: 7.27 and 8.2 volts: Internal resistance is 2.6 ohms.

nexθ

1. intro to gauss law: https://www.youtube.com/watch?v=q78oByOGdjk
```By 4:45:  Have your Mr. Circuit board.
```Either volunteer or nomoninate a report that is better than yours to share with the class.
```Put your name on postit notes I will provide.