Work, Energy, and Electric Field (13th day).

Spring 2015

Professor Mason

April 14 Class

Battery and Bulb Experiment

The first thing we learned in class was about doing an experiment involving two batteries and two light bulbs attached with circuits. We were asked to figure out which one was the brightest and which one was the dimmest, and we had to make a sketch out of it. As we can see on the pictures attached, the batteries that were set up series had the brightest light; on the other hand, the one which was set up parallel had the dimmest light. Parallel set up batteries is more efficient because it gives higher current but lower voltage so it does not take much amount of energy from the batteries; on the other hand, series set up batteries has higher voltage but lower current, and it uses up energy from batteries faster than parallel, but it has brighter light. As for the sketch, we uses symbols as simple as possible as shown in the picture attached.

Joule's Law

In class, we did an experiment about water heater. We needed to know three important things about the water while heating the water, and those are mass, power, and time. The steps are observe change of temperature in water for two minutes, double the voltage, and finally observe the change of temperature for two more minutes. The graph looks like the pictures attached below. 

The red colored graph is a graph showing water at room temperature being stirred, while the blue colored graph shows how crucial the difference is when the water is heated. We found out the equation for Joule's Law is [P = I^2 R], which was broken down from [P = VI] and [P = V^2/R]. We also found out that the definition of Colomb is how charge falls towards other charge in an atom.  

Work done

In class, we discussed things about work done in many functions. We found out that the equation for work done is [W = integral from a to b of F ds]. We were also given a question to calculate by hand about work given a picture of triangle and an object that we were supposed to sketch a diagram first. It turned out to be like the pictures attached above. 

First, we had to figure out what we calculate, which was Wabc equals to the sum of Wab and Wac. We found out that [Wac = F (h/sin 30) *cos60], however, sin 30 and cos 60 cancels out each other, so it becomes F*h; therefore, Wabc = Fh. 

Work as a function of electric field has an equation of [W = integral from a to b of qe E ds]. We also needed to define which one has the biggest work done and the lowest work done based on the picture above; the result was B has the least amount of work done, followed by C and A, which A has the biggest work done. Based on the calculation before, we found out that the work done on each particle [A = q E d], [B = 0 (because line B is perpendicular, thus work is equal to zero], and [C = q E d cos (theta)], which d is distance.  Work is also equals to change of energy (delta U). Potential energy of point charge has an equation of [ q h (Q/r) + C] and potential energy of electrical has an equation of [q k (Q/r)] or [integral from a to b of q E ds]. We also needed to write an equation of voltage based on the potential energy equation above. The result is [V = (k Q)/r] or [V = integral from a to b of E ds], which [V = PE elec/q] were given first; therefore, we just needed to cancel out the q. Work is also equal to [q (V2 - V1)]. Work and Voltage equation as an electric potential energy and electric field has a form of [W = integral from a to b of - q E ds] and [V = integral from a to b of - E ds + C] or [E = dV/ds].

VPython

The last thing we needed to do in class was about VPython. We were given a set of codes for VPython, and we first needed to predict the outcome of that code by sketching a graph. The picture attached shows how it looks like after we predicted the outcome. We also needed to calculate the Voltage by hand by using [V = k q /r], which k is a constant (9x10^9), q is the charge given in the code, r is the distance from the observation location to charge 1 and charge 2. We needed to find V1 and V2 based on the given code.

Next, we needed to create our own code and sketch a graph based on our own code, however, this time we needed to create three charges instead of two. The picture attached below basically shows the foundation of the code in order to create three charges and three observation locations. Then, we needed to calculate the Voltage by hand, therefore, we spend a lot of time calculating from V1 to V3 based on the given code.