In the circuit shown in the figure the capacitor is initially charged to 100 V and the is uncharged. We have to describe in detail how one might charge the capacitor to 300 V by manipulating switches and .

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It is given that initially the capacitor is initially charged to 100 V and the is uncharged. Therefore, an amount of energy

is stored in the capacitor. The switch is closed and the switch is kept open for a time interval that will be determined next. The circuit is then a LC-oscillator with frequency

period

After a lapse of time equal to the energy which was initially stored in the capacitor will be transferred to the 10 H inductor and will be stored in it as magnetic energy. At this stage the switch is opened and the switch is closed. We now have a LC-oscillator with frequency

period

The energy in the when its potential is 300 V will be

In time the 4.5 J energy stored in the inductor will be transferred as electrical energy on to the capacitor and the potential difference across it then will be 300 V.