RC capacitor charging
Switch on the supply and watch the current decay as the capacitor voltage rises.
When a capacitor charges through a resistor, its voltage approaches the source voltage exponentially, while the current decays gradually from its maximum value. The time constant τ = RC sets how fast this happens; after about 5τ the capacitor can be regarded as fully charged.
Capacitor and resistor voltages
The two voltages always add up to the source voltage; recharges automatically after 5τ.
Think about it
With the capacitance unchanged, if the resistance is increased to 2 times its original value, how do the initial current and the charging time change?
The initial current is halved and the time constant becomes 2 times as long, so charging is slower.
Model assumptionsIdeal DC source, resistor and capacitor · Initially uncharged · Wire resistance neglected · Recharges automatically after 5τ
Data log
Set the parameters and click “Record data”. Record several rows with different parameters to plot their relationship and fit a straight line; pause and record at different times to study how a reading changes with time.