PHYS_1010 Lab 2_ Ohm's Law - W24

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Apr 3, 2024

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PHYS*1010 Lab 2: Ohm's Law - W24 Ohmic and Non-Ohmic Circuit Components: Exercise 1: Part A - Resistors: Graph of current vs applied voltage: Sample Calculation of Total Resistance from Graph: Since the slope of the graph is the delta(y)/delta(x) with y being the current and x being the voltage. Meanwhile, the resistance is equal to V/I which is the reciprocal of the slope. Therefore: R total= 1/ slope= 1/0.00082=1220 (Ohm) Based on your plot of Current vs. Voltage, does your circuit follow Ohm's Law? Explain your reasoning. From the plot of Current vs Voltage, the circuit is following Ohm’s law. Since the equation of the Ohm’s law graph is linear which means the equation has a constant slope. Thus, if the voltage increases by 1V the current also increases by a constant amount, which means the resistance will remain constant. Part B - Resistors (2.5 pts) Why is it important to directly measure the current first, before using the voltage drop measurement to calculate the current flowing through the circuit? -It is important to measure the current directly because we can compare the value of current measured through 2 methods the second reason is the current value which is measured directly will provide a more accurate result than calculated using voltage drop across the resistor. However, the variation of voltage drop and resistors can affect the result of the current value if we calculate using the second method. Lastly, the resistors of the circuit are built in series which means the current value will not change through the resistor. Therefore, we can directly measure the current value on the whole circuit without worrying about the parallel circuit will separate the current flow into two different small value.

Based on your Part A and B results, which method produces a more accurate current reading measurement? Why? - The direct measure (Part A) is more accurate than the voltage drop method (Part B). To explain, part A directly measures the current flowing through the circuit while part B relies on the resistance and depends on the condition of the circuit, which will cause the measured values to be less accurate. Exercise 2 - Light Emitting Diodes Part A - LED Current Measurements Graph of Current vs. Applied Voltage -The circuit does not follow Ohm's law. The relationship between current and voltage in an LED is not linear. When a current flows from the Anode to the Cathode of an LED, it has a low resistance and allows current to flow resulting in a high current value on the positive voltage side. When the current goes in the opposite direction (i.e., the cathode is at a higher voltage than the anode), it has a very high resistance and blocks current flow resulting in 0 current values. The Led-based circuit does not follow Ohm’s law in a linear relationship but it is an exponential relationship. Part B - LED Voltage Measurements Graph of Voltage vs. Current from Voltage Drop Measurements

-The two graphs of this exercise are the same. It is expected because the circuit only contains 1 resistor which means the voltage drop across the resistor is the circuit's voltage with the given value of current and resistance. The current value of the circuit remains constant since the resistor is in series with the circuit and the value of the current is calculated by the voltage supply device divided by the total resistance which is equal to R1 (only one resistor in the circuit).

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Exercise 3 Linear and Log Scale Voltage vs Distance Graphs ( 2 pts )

Why did you collect your measurements in both ambient light and dark environments? Was there a difference in the data? Why? (2 pts) -Measurements were taken for both ambient light and dark environments since the equation “I = P / (4r^2pi) indicates the intensity is affected by not only the distance, but also the power or luminous flux of the light source . Also, the photocurrent is directly proportional to the intensity of incident light. Did either data set (ambient or dark) follow the Inverse Scaling Law? Was this expected? -The data set does follow the Inverse Scaling Law. At the same value of distance between the light source and the photodiode, the one with ambient light provides a higher voltage given the value of total resistance remains constant. Therefore, a higher voltage is the result of a higher current value and the higher current value is the higher intensity of light since the current value is transferred from the intensity of light collected from the photodiode. The higher intensity of light results from the higher power of light sources in ambient light compared to dark light. Thus, the data set obeys the Inverse Scaling Law. -On the other hand, given an equal light source, the one with a farther distance will

reduce the intensity of light as well as the current value, which leads to a lower value of voltage as shown in the graph. If neither data set showed agreement with the Inverse Scaling Law provided reasoning/sources of error that may have resulted in this finding Additional Circuits Circuit 1 Circuit 2

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