In the following circuit shown in figure, three diodes are connected each with forward resistance $40 \Omega$ and infinite backward resistance. The current through $100 \Omega$ resistance is

For an ideal diode, in forward and reverse biased condition the resistance is respectively

When an n-p-n junction transistor is used as an amplifier in common emitter mode,

In a transistor (common emitter configuration) the ratio of power gain to voltage gain is ( $\alpha$ and $\beta$ are current ratios)