Science Homework Help

In simple detail, the RC circuit is short for Resistor-Capacitor circuit. When a potential difference is applied across these two elements in series, resistor to capacitor or vice versa, the voltage across the capacitor changes over time. When you measure the voltage across the capacitor(Similar to how you measure voltage across a resistor) you will notice the voltage changing, increasing when charging and decreasing when discharging. The lab manual goes into detail on how the voltage changes (it involves the exponential function e^x) depending on if you’re discharging or charging the capacitor. Remember this is all regarding the voltage across the capacitor.

There is a relationship that tells you the amount of time it takes to reach 67% of the maximum charge across the capacitor when charging OR 34% of the total maximum charge across the capacitor when discharging. This is known as ‘Tau’ and is represented by the Greek letter ‘tau’. Essentially, to calculate this time constant requires you to know the resistance and capacitance in the RC circuit. You will determine both of these in order to get a time constant between 15 – 100 seconds. These will tell you how long it takes to reach either 67% or 34% of the maximum charge of the capacitor. The maximum possible voltage difference across the capacitor is equal to the power supply, so 3.3V or 5V. For example, if you use a 330 micro-Farad capacitor and a 100 kilo Ohm resistor, this will result in a time constant of: 33 seconds. You can use any configuration size of the two elements, however, make sure you follow the instructions in the lab manual.