If ' $\mathrm{n}_{\mathrm{c}}$ ' and ' $\mathrm{n}_{\mathrm{h}}$ ' are the number of electrons and number of holes respectively in a semiconductor heavily doped with phosphorous then

The frequency of two tuning forks A and B are respectively $1.4 \%$ more and $2.6 \%$ less than that of the tuning fork C . When A and B are sounded together, 10 beats are produced in 1 second. The frequency of tuning fork C is

With an alternating voltage source frequency ' f ', inductor ' $L$ ', capacitor ' $C$ ' and resistance ' $R$ ' are connected in series. The voltage leads the current by $45^{\circ}$. The value of ' $L$ ' is $\left(\tan 45^{\circ}=1\right)$

When three capacitors of equal capacities are connected in parallel and one of the same capacity, capacitor is connected in series with the combination. The resultant capacity is $4.5 \mu \mathrm{~F}$. The capacity of each capacitor is