Question

A capacitor has charge $50\mu$ C. When the gap between the plates is filled with glass wool 120 $\mu$ C charge flows through the battery. The dielectric constant of glass wool is :

• A. $3.4$
• B. $1.4$
• C. $2.4$
• D. none of these

Answer 1

The correct option is A $3.4$

Before filled wool the charge on capacitor is $Q$
After filled wool the charge on capacitor is $Q^{\prime }=kQ$ where $k=$ dielectric constant.
So charge flow through the battery is $Q^{\prime }-Q=120\Rightarrow Q^{\prime }=120+Q=120+50=170$
thus,$kQ=170\Rightarrow k=\frac{170}{50}=3.4$