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# G485 Charging Capacitor Question

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Why bother with a post grad course - waste of time? 17-10-2016
1. http://www.ocr.org.uk/Images/144793-...of-physics.pdf
Q1)ii)2)
It asks for a sketch of the charging capacitor. I drew an exponential tending to a certain value. However, the mark scheme is awarding a mark for drawing a straight line. As far as I'm aware capacitors charge and discharge exponentially. The only reason I can see that the line is straight would be due to the variable resistor present alternating its resistance to ensure it charges at a constant rate?
Would this be correct?
I'm a little foggy on capacitors, so when the question says current remains constant, is that a dead giveaway it'll charge at a constant rate? When a capacitor charges exponentially, does current decrease exponentially then?
2. (Original post by Danny.L)
http://www.ocr.org.uk/Images/144793-...of-physics.pdf
Q1)ii)2)
It asks for a sketch of the charging capacitor. I drew an exponential tending to a certain value. However, the mark scheme is awarding a mark for drawing a straight line. As far as I'm aware capacitors charge and discharge exponentially. The only reason I can see that the line is straight would be due to the variable resistor present alternating its resistance to ensure it charges at a constant rate?
Would this be correct?
I'm a little foggy on capacitors, so when the question says current remains constant, is that a dead giveaway it'll charge at a constant rate? When a capacitor charges exponentially, does current decrease exponentially then?
Yeah it's a straight line because current is constant - watch out for questions saying constant current (cos it seems to happen quite often at A level)

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