A diode has Zener voltage of 10 V and maximum power dissipation of 0.5 W , then the minimum resistance to be used in series with this diode for safety when it is connected to a 25 V power supply is $\_\_\_\_$ $\Omega$.

A voltage regulating circuit consisting of Zener diode, having break-down voltage of 10 V and maximum power dissipation of 0.4 W , is operated at 15 V . The approximate value of protective resistance in this circuit is $\_\_\_\_$ $\Omega$.

A potential divider circuit is connected with a dc source of $$20 \mathrm{~V}$$, a light emitting diode of glow in voltage $$1.8 \mathrm{~V}$$ and a zener diode of breakdown voltage of $$3.2 \mathrm{~V}$$. The length (PR) of the resistive wire is $$20 \mathrm{~cm}$$. The minimum length of PQ to just glow the LED is _________ $$\mathrm{cm}$$.

From the given transfer characteristic of a transistor in $$\mathrm{CE}$$ configuration, the value of power gain of this configuration is $$10^{x}$$, for $$\mathrm{R}_{\mathrm{B}}=10 ~\mathrm{k} \Omega$$, and $$\mathrm{R}_{\mathrm{C}}=1 ~\mathrm{k} \Omega$$. The value of $$x$$ is __________.