電容capacitor

The specification of "10-volt" on the capacitor is the maximum voltage that the capcitor can stand without its insulation to be broken down.
Hence, a voltage of 25 volts surely will break the dielectric in the capacitor and render it useless.
The answer to you MC is therefore option D
那如果我用 3V直流電源為它充電 , 再斷開 , 會有什麼事發生??
The capacitor is charged, but the charges stored in it will now become
(3/10) x 500 x 10^-6 coulombs = 150 x 10^-6 coulombs = 150 uC
如果將該電容器 , 串聯接駁一個 1000歐姆的電阻器 才充電 會不會燒??
If you use a 25v power source, but connect a 1000-ohm resistor in series in the charging circuit, the capacitor still breaks. The resistor only lengthen the time of charging because it limits the current. When the voltage across the capacitor reaches to over 10v, it will break.

25V供入10V電容，實立刻燒毀該電容啦。
至於用3V直流電供入10V電容，就根本供不入(即不能充電)；未達500 x 10^-6時就已停止了，無法回電產生交流頻率。