A capacitor begins charging through a resistor from an ideal DC source at
PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A capacitor begins charging through a resistor R from an ideal DC source at t=0. Exactly at t=2τ (where τ=RC for the original circuit), the resistor is instantly replaced by a second resistor of value R/2 while the capacitor continues to charge from the same source. Which qualitative change occurs in the current-versus-time graph immediately after the switch to the smaller resistor?
(a) The current becomes roughly twice its value just before the switch and then decays with a shorter time constant.
(b) The current remains continuous and continues decaying with the original time constant.
(c) The current becomes roughly twice its value just before the switch and then decays with the original time constant.
(d) The current decreases further because reducing R increases the overall time constant.