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In a semiconductor,

(a) | there are no free electrons at \(0~\text{K}.\) |

(b) | there are no free electrons at any temperature. |

(c) | the number of free electrons increases with temperature. |

(d) | the number of free electrons is less than that in a conductor. |

1. (a), (b)

2. (b), (c)

3. (a), (c), (d)

4. (a), (b), (d)

Subtopic: Â Energy Band theory |

Â 89%

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When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor,

1. increases

2. decreases

3. remains the same

4. becomes zero

Subtopic: Â Types of Semiconductors |

Â 84%

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A \(\mathrm{p}\text-\)type semiconductor is:

1. | positively charged |

2. | negatively charged |

3. | uncharged |

4. | uncharged at \(0~\text{K}\) but charged at higher temperatures |

Subtopic: Â Types of Semiconductors |

Â 60%

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Let \(n_{p}\) and \(n_{e}\) be the number of holes and conduction electrons in an intrinsic semiconductor. Then:

1. \(n_{p}> n_{e}\)

2. \(n_{p}= n_{e}\)

3. \(n_{p}< n_{e}\)

4. \(n_{p}\neq n_{e}\)

Subtopic: Â Types of Semiconductors |

Â 86%

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The peak voltage in the output of a half-wave rectifier is \(30 ~\text{V}.\) The rms voltage of the output wave is: (assuming no distortion in wave)

1. \(\frac{30}{\sqrt2}~\text{V}\)

2. \(15 ~\text{V}\)

3. \(\frac{15}{\sqrt2}~\text{V}\)

4. \(10 ~\text{V}\)

1. \(\frac{30}{\sqrt2}~\text{V}\)

2. \(15 ~\text{V}\)

3. \(\frac{15}{\sqrt2}~\text{V}\)

4. \(10 ~\text{V}\)

Subtopic: Â Rectifier |

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Assume that the threshold voltage of a diode is \(0.7\) V, and the forward resistance is negligible.

The current through the circuit is:

1. \(40\) mA

2. \(54\) mA

3. \(33\) mA

4. \(26\) mA

The current through the circuit is:

1. \(40\) mA

2. \(54\) mA

3. \(33\) mA

4. \(26\) mA

Subtopic: Â PN junction |

Â 54%

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The band gap between the valence band and the conduction band in a certain material is \(3\) eV. What is the longest wavelength of light that can create an electron-hole pair in the material, with the electron in the conduction band and the hole in the valence band? (Take \(hc\) =\(1240\) eV-nm.)

1. | \(414\) nm | 2. | \(300\) nm |

3. | \(830\) nm | 4. | \(207\) nm |

Subtopic: Â Energy Band theory |

Â 87%

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A \(\mathrm{p\text-n}\) junction has an electric field of \(6\times 10^{5}\) V/m in the junction and the junction width is \(500\) nm. The height of the potential barrier is:

1. \(0.6\) V

2. \(0.3\) V

3. \(0.5\) V

4. \(0.25\) V

1. \(0.6\) V

2. \(0.3\) V

3. \(0.5\) V

4. \(0.25\) V

Subtopic: Â PN junction |

Â 91%

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The current-voltage characteristic of an ideal \(\mathrm{p \text{-}n}\) junction diode is given by the graph as shown in the following figure:

This diode is connected with a resistance of \(5~\Omega\) in series with it as shown below:

Which of the following shows the dependence of the voltage \(V_{AB}\) and the current \(i\), when the diode is forward-biased? (\(V_{AB}\) in volt, \(i\) in ampere)

This diode is connected with a resistance of \(5~\Omega\) in series with it as shown below:

Which of the following shows the dependence of the voltage \(V_{AB}\) and the current \(i\), when the diode is forward-biased? (\(V_{AB}\) in volt, \(i\) in ampere)

1. | \(V_{A B}=i\cdot5+0.6\) |

2. | \(V_{A B}=i\cdot5-0.6\) |

3. | \(V_{A B}=i\cdot5+(0.6-5)\) |

4. | \(V_{A B}=i\cdot5+\left(0.6+5\right)\) |

Subtopic: Â PN junction |

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The voltage \(V_{AB}=20~V\) at its peak value, and is sinusoidal in time. The current \(i\) (in amperes), when plotted as a function of time, is given by:

(Consider the diodes as ideal.)

(Consider the diodes as ideal.)

1. | 2. | ||

3. | 4. |

Subtopic: Â PN junction |

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