<img src="https://static.zxtiku.com/wangke/imgs/topic/074a87c7a3a155e086d7be0416421a04.png"/>充电电路如图所示，若电源<img src="https://static.zxtiku.com/wangke/imgs/topic/547a7f8ce3b7994084860f840faca873.png"/><img src="https://static.zxtiku.com/wangke/imgs/topic/a4a27fb118ec01c6b72a96d04bd10b0e.png"/>，<img src="https://static.zxtiku.com/wangke/imgs/topic/cd098402402eed30c5b96455d6aaee7b.png"/>，则电容电压的表达式为（），<img src="https://static.zxtiku.com/wangke/imgs/topic/5652deff9e574afaa3365073143c7e75.png"/>。<br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/5c35c7c6f3d02de4c1d449066f2c39e0.png"/>