Spring 2015
Professor Mason
April 21 Class
Electric Potential in Diagram
The first thing we did in class was about analyzing sketch or diagrams of how electric potential in a set of batteries and light bulbs. For the first sketch in the picture shown below, we were asked what would happen to light bulb #1, #2, and #3 if the switch next to light bulb #2 is turned on. The answer is when the switch is turned on, light bulb #1 would light brighter, light bulb #2 would light dimmer, and finally light bulb #3 would not light at all. It happens because (Electric Potential in each batteries is 1.5V) the positive charge of the battery goes through light bulb #1 first, so that light bulb #1 would light brighter. Then, both electric potential that went through bulb #1 and #3 cancels each other out; therefore bulb #2 would not light at all. The same method also applies for the second sketch; we were asked to predict what would happen to each light bulb. The result was that light bulb #1 and #2 light the same because they both have equal electric potential running through the bulbs.
Voltage Law and Current in Batteries
In class, we learned Voltage Law based on the lab manual. We found out that the definition of Voltage Law is the sum of voltages around the circuit equals to zero [sigma V = 0] (as shown in the picture above); another word for Voltage Law is Vin - Vout = 0. The same equation for Current Law goes the same as Voltage Law, which is the sum of amperes around the circuit equals to zero [sigma I = 0].
We also did a question based on the lab manual, which asked for how the bulb and batteries would set up in terms of dim and bright. The result for that question is shown in the picture attached above. Series setup of bulbs would make the bulbs light dimmer; however, series setup of batteries would make the bulbs light brighter. On the other hand, parallel setup of bulbs would make the bulbs light brighter; however, parallel setup of batteries would make the bulbs light dimmer. We also found out an equation in terms of voltage and current is [P = IV], which P is the brightness, I is the current, and V is the voltage.
Color Bands in Resistors
In class, we learned that resistors use color bands to identify their values instead of using numbers because placing numbers in the resistor would be really small and really hard to read. We also learned how to read the numbers in resistors based on the colors given. We learned that: we have to read the band from left to right; Color band 1 resembles the first digit (Ex: 4), color band 2 resembles the second digit, color band 3 resembles the multiplier (Ex: x10^2), and finally color band 4 resembles the uncertainty (Ex: plus or negative 2). We also learned that in order to measure a series or parallel of resistors, we have to twist the end of each resistors together to combine them together. Resistance in series setup adds together (sum), while resistance in parallel is multiplier or divider depends on how many resistors there are (2 resistors: divide the result by 2, 3 resistors: divide the number by 3). We measured each resistors by using the machine shown in the picture attached on the left. We placed the two very tip of the wires to the end of each resistors in order to measure them. For experiment, we were given four different resistors; we needed to measure each one of them, and the results are shown in the picture below.
To answer the question "Did your resistor match the color coded value with uncertainty?", the answer is yes, they all matched the color coded value with uncertainty.
Kirchhoff's Law
After we learned the lecture from Professor Mason, we found out that Kirchhoff's Law is about loop in a sketch. We also learned that in parallel setup, I in (flow in) is equal to I out (flow out) in a loop. Two easy steps to learn the basic of Kirchhoff's Law is first, we have to assign the currents, then followed by applying loop rule for each loop. We also know for sure that the flow going up is most likely positive, and the flow going down is most likely negative. The three basic equations for the setup below are: [V1 - I2 R2 - I1 R1 = 0], [I2 R2 - I3 R3 - V2 = 0], and [Current = I1 = I2+I3], based on the variables given around the setup. Equation may vary depending on the setup. These equations are based on one equation, which is [V = IR].
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