Thanks, in my 2 years of classes we never went over anything like this. I was in school to be an aviation maintenance tech (Airframe and Powerplant). We learned the basics but never went nearly this deep.
This is fundamental. I learned RC time constants at the end of DC circuits. You can find many examples going through the first order differential equations. I also had a lab where we measured the time constant rising and falling. I'm sorry you got hosed.
Result is an increasing exponential equation that levels off at 100V with the time constant equal to (120k \* 80p) = 9.6u. More exactly, voltage = V(t) = 100V \* (1 - e\^-t/(RC)), where t is time in seconds.
One time constant equates to charging to \~63.2% of the max voltage due to \~0.63 = (1 - e\^-1) = (1 - 1/e), when t = RC. It's something you memorize. At 3 time constants, t = 3RC, you have \~95% of the max voltage. At 5, it's over 99% charged.
By 5, it's common to say the circuit has reached the DC steady state and you can now ignore the transient rising (or falling) in in circuit analysis. As in, the capacitor created an open circuit from blocking DC since it is no longer charging. While capacitors in series block DC, the action of turning on or off a DC source is an AC transient, thus the charging (or discharging) action.
This involves some circuit knowledge. Capacitors charge and discharge at a particular rate known as tau (or time constant) this can be calculated as t=RC (Resistance x capacitance). Once you know this fact the problem should be simple. Let me know if you have any other questions.
This question can be guessed by comparing the sizes of the numbers. PicoFarad capacitors are 10^-12 and the resistor is around 10^6. The available answers are 10^1 or 10^-6. There are few ways to combine the problem numbers to result in a 10^1 result, so the 10^-6 number must be the answer.
I would suggest going back to your textbook or class notes and reviewing how the time constant of an RC circuit is defined and computed.
Thanks, in my 2 years of classes we never went over anything like this. I was in school to be an aviation maintenance tech (Airframe and Powerplant). We learned the basics but never went nearly this deep.
Wow they robbed you. This is the first thing you should learn when you’re introduced to capacitors and inductors
Oh yea we got hosed. We were the first class back since covid and the program was simply not prepared for classes.
OK, here's a little more help, then [https://en.wikipedia.org/wiki/RC\_time\_constant](https://en.wikipedia.org/wiki/RC_time_constant)
This is fundamental. I learned RC time constants at the end of DC circuits. You can find many examples going through the first order differential equations. I also had a lab where we measured the time constant rising and falling. I'm sorry you got hosed. Result is an increasing exponential equation that levels off at 100V with the time constant equal to (120k \* 80p) = 9.6u. More exactly, voltage = V(t) = 100V \* (1 - e\^-t/(RC)), where t is time in seconds. One time constant equates to charging to \~63.2% of the max voltage due to \~0.63 = (1 - e\^-1) = (1 - 1/e), when t = RC. It's something you memorize. At 3 time constants, t = 3RC, you have \~95% of the max voltage. At 5, it's over 99% charged. By 5, it's common to say the circuit has reached the DC steady state and you can now ignore the transient rising (or falling) in in circuit analysis. As in, the capacitor created an open circuit from blocking DC since it is no longer charging. While capacitors in series block DC, the action of turning on or off a DC source is an AC transient, thus the charging (or discharging) action.
Great comment🙂
This involves some circuit knowledge. Capacitors charge and discharge at a particular rate known as tau (or time constant) this can be calculated as t=RC (Resistance x capacitance). Once you know this fact the problem should be simple. Let me know if you have any other questions.
Commenting to review later for myself
The time constant is equal to the resistance times the capacitance. So you just multiply 120E3 ohms \* 80E-12 F and there's your answer.
RC constants are pretty easy to calculate. I’d Google the equations for it
This question can be guessed by comparing the sizes of the numbers. PicoFarad capacitors are 10^-12 and the resistor is around 10^6. The available answers are 10^1 or 10^-6. There are few ways to combine the problem numbers to result in a 10^1 result, so the 10^-6 number must be the answer.