Question

Capacitor question. Image attached.

Answer 1

When charging a capacitor with a voltage source, the voltage at the capacitor will be 63.2% of the final voltage after the time τ has passed. As you correctly wrote down τ = RC - meaning you can calculate C after determining τ from the graph.

The charge in the capacitor is \[Q = C \, V_b \left[ 1 - e ^{-\frac{t}{R\,C}}\right]\]
It is important that you not only determine τ and C, but also try to understand why charging with a constant voltage happens in this way. I'm sure your textbook will explain :)