Ok guys can I put my 2bob’s worth in?

I will put some test in that were done it may help.

What was not stated in this series circuit was the value of the coil, its DC resistance and impedance XL and the same for the Capacitor.

To get things correct you will need to know them or measure them, calculate whatever.

On a stable 12V Dc supply with a coil and a cap in series, that is it is switched on and left on.

The voltage will show a high peak across the coil then will be 12v the current will rise as shown extensionally, opposing the input, and it will lag.

At the T point this is one time constant, it will get to 63% after 5time contents it will be fully ‘charged’ yes it will hold a charge, once it gets there it will allow full current to flow in the circuit to charge up the cap to again 5time contents. Then current will stop if the capacitor is a good one and does not ‘leak’. The voltage will equal the supply voltage of 12VDC.

Now if you disconnect the power supply, extremely fast, if it is a switch there will be an arc as the coil tries to discharge across the gap, the voltage on the cap cannot as the coil will oppose it as if it was the supply like the battery.

There will now be some lost charge in the coil, its voltage will be lower than the cap, so now the cap take the place of the battery and tries to charge up the coil, again it will take time to do this, another 5 time constants of what is left of the voltage.

Now we have a problem, the coil is charged, so what now, the coil has a DC resistance, this will try to discharge, ‘leak’ the capacitor, now the reverse and it starts again, this is known as ringing.

Here are some test circuits if they come out .

T is calculated by in a coil L/R L in henneries and R in DC resistance this is T and one time content for the coil to get to 63% of the max current, 5 T and it is fully charged.

Remember if XL=XC then the current in the circuit will be V/R dc resistance

there is one for Bob Boyce test will put in BB

Have fun

Brian