Week 7 day 2

Lecture

Rage Bridge Discussion, why large sparks occurs when the circuit is initially plugged in in dc circuit

Second activity calculating capacitance and unit of permittivity constant

Best part of the lecture: blowing up electrolytic Capacitor by plugging the wrong polarity demonstration

Calculating potential difference across RC circuit with constant DC current source, assuming it have been plugged in for a long time

Next activity is to calculate the equivalent capacitor of a circuit, capacitor on series is calculated like resistors in parallel, and vice versa :

Calculating current and voltage relations on Inductor, potential difference across inductor is equal to the product of the time derivative of current through the inductor and its inductance (L)

Capacitor Voltage- current Relations Lab

Pre-Lab :

We have to predict what happen to the voltage versus of time and current versus time on an RC circuit:

 WE measured our actual value of capacitor and resistor:

The view of our RC circuit, to measure the current across capacitor, we scope the voltage difference across resistor and divide it by the value of resistance :

Our first input we use 1KHz frequency of cosine wave:

Scope output blue line represent the voltage across the capacitor, the red line represents  current on the resistor and capacitor,  and the yellow line is equal to the voltage across the 100-ohm resistance:

here we observe a phase shift of pi/2 between the current that flows through and the voltage across the capacitor.

we redid our calculation with a 2KHz cosine wave:

Here we still notice phase shift of pi/2 between the potential difference across and the current flowing through the capacitor. The 2K hertz occurs more frequently since the period it took the sinusoidal current is reduced by half.

Lastly, we change our input voltage with a 100Hz triangular input:

Here in the oscilloscope window, we have 3 graphs: the blue line represent the input voltage, red line represent the current flows through the capacitor and resistor and yellow line represents the voltage across the resistor. Here we observe that the graph of current flows through the capacitor is a square wave. The current have a constant positive value when the slope of voltage input is positive, and a constant negative value when the input voltage is negative.

Inductor Voltage- Current Relations Lab

In this Lab, we replaced our capacitor from our previous circuit with an inductor. Our LC resistor is shown by the picture below:

we inputted a 1KHz Blue line represented our input voltage, the yellow line represented the voltage across the resistor and redline represent the current that flows through the resistor.  We observe a phase shift of negative pi/2  between the input voltage and current through resistor:

We repeated the same procedure with the circuit with 2 KHz input voltage:

Summary

In our lecture, we learn about using capacitor and inductor as part of our circuit. According to the passive sign convention current always flow toward the positive side of inductor and capacitor while leaving the negative side. Capacitor stores energy through Electric field.Capacitor resists potential change.When capacitor acted as a wire when it has no initial charge and acted as an open circuit when it's fully charged  The current flows through the capacitor is equal to the product of its capacitance and its derivative of the voltage across over time. The capacitance of inductor is related to its geometrical shape. The most current used capacitor is parallel plate capacitor that uses a metal plate, mostly aluminium foil separated by an insulator. The most common capacitor, the electrolytic capacitor is polarised, that means the positive terminal have to be hooked up to the positive voltage, or we can risk blowing up our circuit. Inductor stores Energy through its magnetic field. Inductor resists a current change, the potential difference of inductor is equal to the product of its inductance and its derivative of current over time.