Hi there 
Just wondering how would you explain a capacitor discharge graph for voltage. I would start it like this,
As a capacitor discharges, the repulsion between the like charges on the capacitor plates causes charge to flow from the capacitor into the circuit. As Q=CV, as Q decreases, V decreases (Capacitance is constant)
How would I explain why the graph is an exponential decay graph? Thank you
Hi and welcome to Studyit!
You have just about answered your own question: as the amount of charge decreases, so does the voltage, so the rate at which charge leaves the plates decreases (V=IR). The graph is therefore exponential, not linear.
Thank you So how would we explain why the rate of charge decreases?
Hi, the rate at which charge leaves the plates decreases because the voltage drops as charge leaves the plates, so the current also drops since V=IR, and this means the rate at which charge leaves the plates further decreases.