Student Ramuel Mendoza Raagas  for Teaching Fellow Ronald Newburgh, Ph.D. 

Physics E1b Electromagnetism  PreLab for Experiment #2: Direct Current Circuits  Spring Term 2003 

In physics, zero is no mere empty basket. Invented by Indian civilization, the zero is an allimportant, notmerelytrivial number which opens new worlds, even perhaps more so than infinity itself.
If the greatest ENglish bard ever wrote rthe masterpiece Much Ado About Nothing, it might be quite a lucrative project to work on a layman's science book by the title Much Ado about Zero. Zero, in, our universe is a broad governing force.
Electrical circuits are often quite circuitous means, of ideally, boiling down to zero. When circuits progress into more compound concatenations, we often can resort to looking for the zero that will be our guiding light. Well, it's not just in direct current circuits, even in the pedagogically prior topic of electrostatics, the zero turns up like a rising sun often enough. Even, later down in the topic of electomagnetism where currents fuse the curl, gradient and derivate terms of magnetic field B and Electric field E into commontimespace equations, the ubiquitous zero will help out in eliminating one component of terms from an adjacent one, making the calculations of line and surface integrals less cumbersome, and, in fact, more manageable.
In electrostatics, and the entirely separate phenomenon of magnetostatics (Yes, without current, which would serve as a common household, electricty and magnetism are separate individuals each minding its own pool of properties.) it was Maxwell's equations that gave us our zero's. Electrostatics has zero as
We will look into two of Kirchoff's most fundamental rules: the loop and junction rules.
All in all, we will build eight circuits with switches. This experiment has two parts: the first qualitative, the second quantitative. The qualitative part establishes equality and inequality relations in current flow (as evidenced by light bulb glow, which we need not quantify in terms of candelas). Part one's four circuits will have each between one and three light bulbs. Part two will also have us concerned with magnitude of current (directional flow of current as becomes a task in itself in more complex dibattery Kirchoof jointloop circuits will not yet be a concern). This time, however, we will not settle with ascertaining current at a glance,
Still, once the class of manufactured light is established, whether it be fluorescent or incandescent, and our lab does use incandescent bulbs as these, when fresh, are transparent enough, so that through their thin but eggdurable glass encasings we have a better than aquarium view of the filament and its very proppingstands inside does higher Wattage (power rating) mean stated for a bulb denote its relative brightness within its given class?
Two of the three standard equation relations for electrical power in directcurrent circuits have current figured in as a factor. P = IV is one. P = I^{2}R, since V from the prior equation may be drawn out as IR, V = IR being another standard established relation.
Somewhat likewise, two of the these figure in voltage (potential difference) as a factor (once as itself; the other instance of expression has it embedded squared). However, the latter pointm establishes that expressibility of R < expressibility of I = expressibility of V.
A = B > F when switch 2 is open while switch 1 is closed, as the body text has indicated for mimicking Circuit 2.
When both its switches are thrown shut however, Circuit 4 may well be regarded as Giancoli's Figure 269 given a quarterrotation clockwise. Hence, for our question 14 I will just rephrase Ginacoli's response that A > B = F, because the current running down Circuit 4 is bifurcated at junction point a into equal parts, such that current through B equals current through F which add up to what was current through A. Kirchoff's junctionm
18. 12.7 milliAmperes
19. Circuit 5's voltmeter will read a shade less than 6.5 volts
20. The power dissipated will amount to 0.0829 Watts.
I^{2}R is preferable a power calculation than IV within this context, because we want to emphasize the role as factor of a resistance, R_{1}, that is.
21. 13 milliAmperes will flow through CIrcuit 6's ammeter.
22. I predict that the voltage drop (V_{ab}) across R_{2} would amount to 2.6 Volts, using V = IR for my calculation.
23. I predict that the voltage drop (V_{bc}) across R_{3} would amount to 3.9 Volts, again using V = IR for my calculation.
24. V_{battery} = V_{bat} = V_{ab} + V_{bc} = V_{ac}
25. I predict that the current (I_{4}) through resistance R_{4} would amount to .0216 amperes.
26. I would predict that the current (I_{5}) through resistance R_{5} would amount to .0127(451) Amperes.
27. I would predict that the current (I_{total}) through the battery would amount to .0344 Amperes.
28. I_{5} + I_{5} = I_{total}
29. 189 Ohms
X_{C} units  = 

= 

= 

= 
When we refer to either a capacitor or an inductor as being a "short" for a certain orientation of frequency (as the kind of thing we get Urone's Figure 22.44(b), where the capacitor shorts out high frequencies from a lefthand "blackbox" circuit to ground, so as to deprive them from getting to the righthand circuit), we would like to think of the component as, in effect, causing a short circuit (as contrasted to an open circuit) dishing off to ground a certain quality of wavefrequqency being fed into a circuit in which it has been installed.
What a fuse is to current, a nonresistor reactancecomponent is to frequency, and yet inductors and capacitors are ministers of a taller order against frequency extremities when compared to the footsoliders that are fuses, which are like bees that sting to kill audacious uprisings of current, only to themselves ending out used up.
Consulting Tipler (Chapter 31 Section 3 page 962 Volume 2, Physics, Freeman), we find that the capacitor is indeed a short for high frequencies. The inductor shorts out both direct current and lowfrequency alternating currents. This summary goes well with calculations of reactance. A capacitor becomes an open (rather than short) circuit with low frequencies that bend the reactance calculation's denominator so low that the numerator's mere value of one can end up translating into great achievements of reactance making the capacitor a dead end to the alternating current.
10 Hertz  15,915 like sixteen kiloohms  W Ohms 
200 Hz  795.77 W  
300 Hz  530.52 W  
400 Hz  397.89 W 
1000 Hertz  W Ohms  
10000 Hertz  W Ohms  
100000 Hertz  W Ohms  
10000000 Hertz  W Ohms 
100 Hertz  W Ohms  
500 Hertz  W Ohms  
1000 Hertz  W Ohms  
10000 Hertz  W Ohms  
100000 Hertz  W Ohms  
10000000 Hertz  W Ohms 