In a good conductor, the energy gap between the conduction band and the valence band is
1. Infinite
2. Wide
3. Narrow
4. Zero

A Ge specimen is doped with Al. The concentration of acceptor atoms is $~{10}^{21}$ $\mathrm{atoms}/{\mathrm{m}}^3$. Given that the intrinsic concentration of electron hole pairs is $~{10}^{19}/{\mathrm{m}}^3$, the concentration of electrons in the specimen is:

In a semiconducting material, the mobilities of electrons and holes are ${\mathrm{\mu }}_{\mathrm{e}}$ and ${\mathrm{\mu }}_{\mathrm{h}}$ respectively. Which of the following is true?
1. \(\mu_{e} > \mu _{h}\)
2. \(\mu_{e} < \mu _{h}\)
3. \(\mu_{e} = \mu _{h}\)
4. \(\mu_{e} <0; ~\mu _{h}>0\)

The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current?

1. 1.5 $\mathrm{\Omega }$ 

2. 5 $\mathrm{\Omega }$

3. 6.67 $\mathrm{\Omega }$

4. 200 $\mathrm{\Omega }$

How much is the forbidden gap (approximately) in the energy bands of germanium at room temperature? 
1. \(1.1~\text{eV}\)
2. \(0.1~\text{eV}\)
3. \(0.67~\text{eV}\)
4. \(6.7~\text{eV}\)

Two PN-junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be:

In a PN-junction diode:

Pure Si at 500 K has equal number of electron $\left(n_{\mathit{e}}\right)$ and hole $\left(n_{\mathit{h}}\right)$ concentration of $1.5\times {10}^{\mathrm{16 }}{\mathrm{m}}^{-3}.$ Doping by indium increases $n_{\mathit{h}}$ to $4.5\times {10}^{22}$ ${\mathrm{m}}^{-3}.$ The doped semiconductor is of:

If in a p-n junction, a square input signal of 10 V is applied as shown, then the output across R_L will be:
              

1.		2.
3.		4.

In the given figure, the potential difference between A and B is: