Question

Three capacitors of capacitances 3μF, 9μF and 18μF are connected once in series and then in parallel. The ratio of equivalent capacitances in the two cases(C_S/C_P) will be

• A. (a) 1 : 15
• A. (b) 15 : 1
• A. (c) 1 : 1
• A. (d) 1 : 3

Answer 1

(a)

$C_{P} = 3 + 9 + 18 = 30\mu F$

$\frac{1}{C_{S}} = \frac{1}{3} + \frac{1}{9} + \frac{1}{18} = \frac{1}{2}$

$\therefore$ $C_{S} = 2\mu F$

Now $\frac{C_{S}}{C_{P}} = \frac{2\mu F}{30\mu F} = \frac{1}{15}$