Hi there I'm still plugging away at this nightmare. Ill attach a picture of the question, I've highlighted it as I've scribbled around it and I can't figure it out. I understand the time constant is the time taken for charge/voltage to fall to 37% of initial figures. But it doesn't seem to work here...where am I going wrong!
Hi there I'm still plugging away at this nightmare. Ill attach a picture of the question, I've highlighted it as I've scribbled around it and I can't figure it out. I understand the time constant is the time taken for charge/voltage to fall to 37% of initial figures. But it doesn't seem to work here...where am I going wrong!
The voltage across the capacitor is falling hence discharging.
V(t)=V(t=0)(e(CR−t))
Your task is to make CR the subject and substitute the known values where:
Hi there I'm still plugging away at this nightmare. Ill attach a picture of the question, I've highlighted it as I've scribbled around it and I can't figure it out. I understand the time constant is the time taken for charge/voltage to fall to 37% of initial figures. But it doesn't seem to work here...where am I going wrong!
I know this isn't especially helpful in general, but in an exam like this my thinking would go:
time taken to halve = 48 ms therefore time taken to quarter = 96ms the time taken to get somewhere in between a half and a quarter (37% or whatever), must be between 48 and 96 ms.
You only have one option that's around there, so in an exam this would be quicker than calculating it. Of course, you should still learn how to work it out (although if you're doing AQA the formula is given to you).