Lab Report

Topics: Electric charge, Resistor, Ohm's law Pages: 5 (1453 words) Published: April 7, 2013
Ohm’s Law II


The purpose of this experiment is to demonstrate how non-ohmic devices respond on a direct circuit. Furthermore, we also explored their behavior when they were connected in different configurations. In order to accomplished this we used a capacitor, diode, resistor, and battery. We ran a series of experiments that generated graphs and equations, which can explain the relationship between voltage and time for capacitors and diodes. Non-ohmic resistors are also referred to as non-linear because a plot of voltage vs. current for such a resistor will not be a straight line. These graphs also exemplified non-ohmic devices express no resistance, and can have a variety of applications on our daily lives. Furthermore, results obtained during this experiment showed us the relationship between voltage and time on a capacitor. On the graphs we can appreciate how the capacitor quickly looses its voltage after being charged and then disconnected. Hence, indicating that in a direct circuit unit the current is one directional, meaning it only travels in one direction. Similarly, a capacitor stores voltage, and it does not matter if we change the direction of the current, as it will only be functional in one direction.

A capacitor consists of two Conducting Plates separated by an insulating material or dielectric. Figure 1 and Figure 2 are the basic structure and the schematic symbol of the capacitor respectively. During this experiment we charged a capacitor to 5V, we allowed to charge by letting it run for 4-5 minutes before disconnecting it from the power supply.
Figure 1: Basic structure of the Capacitor Fig2: Point circuit diagram We first did this with a 6uF capacitor and recorded the time it took to discharge, and then we proceeded to repeat the experiment with a 100uF capacitor. The capacitor was connected to a circuit with Direct Current (DC) source, two processes, which are called “charging” and “discharging” the capacitor. In Figure 3, the Capacitor is connected to the DC Power Supply and Current flows through the circuit. Both Plates get the equal and opposite charges and an increasing Potential Difference, vc, is created while the Capacitor is charging. Once the Voltage at the terminals of the Capacitor, vc, is equal to the Power Supply Voltage, vc = V, the Capacitor is fully charged and the Current stops flowing through the circuit, the Charging Phase is over. VR= Voltage resistance

RC= Resistance of circuit
V= Voltage
C= circuit
IC=Current of circuit
VC= Voltage of Circuit
VR= Voltage resistance
RC= Resistance of circuit
V= Voltage
C= circuit
IC=Current of circuit
VC= Voltage of Circuit

Figure 3: The Capacitor is Charging
For the second part of the experiment, we used wooden circuit board and set it to the same voltage as the one we used for the capacitor (5V). Then we reversed the leads for the power source such that the direction of the current through the circuit was reversed. Furthermore, we use the RLC circuit board, in order to use the 100 ohms resistor, then we applied 5V to the circuit and switched the direction just as we did on the latter board. Finally, we went back to the wooden board and connected the circuit with a Zener diode. Then, we measured the voltage across the resistor while using the PASCO interface to look at the output voltage and the voltage across the resistor. Theory:

Electrical current is the amount of charge passing by a given point in a conducting path (circuit) per unit time: I= dQ/dt. It is agreed for convenience that the direction of the current is the same as the direction of movement of positive charges in electric field. In a metallic conductor, such as a wire, the only mobile particles are negatively charged electrons, which move in a direction opposite to that chosen for the conventional current. Ohm's law states that the current I that flows in a circuit is directly...
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