Q. No.A photocell is illuminated by a point source of radiation \(4\) m away. If the same source is kept \(8\) m away, then the number of photoelectrons emitted:
1.
becomes four times the initial value.
2.
becomes one-fourth of the initial value.
3.
remains unchanged.
4.
becomes half of the initial value.
A Zener diode is used to obtain a constant voltage. If applied voltage \(\text V\) changes, then:
(\(\text V\) is more than Zener voltage)
| 1. | \(i_{1}\) and \(i_{2}\) change. |
| 2. | \(i_{2}\) and \(\text V_{0}\) change and \(i_{3}\) remains constant. |
| 3. | \(i_{2}\) and \(\text V_{0}\) don't change while \(i_{3}\) changes. |
| 4. | \(i_{3}\) and \(\text V_{0}\) don't change while \(i_{2}\) changes. |
Which of the following-junction is used unbiased?
1. Photo diode
2. LED
3. Zener diode
4. Solar cell
1. \(36~\text{mW}\)
2. \(12~\text{mW}\)
3. \(144~\text{mW}\)
4. \(72~\text{mW}\)
The \((I\text-V)\) characteristics of a \(\mathrm{p\text-n}\) junction diode is as shown. If \(R_1\) and \(R_2\) be the dynamic resistance of the \(\mathrm{p\text-n}\) junction when (i) a forward bias of \(1\) volt is applied and (ii) a forward bias of \(2\) volts is applied respectively, then \(\frac{R_1}{R_2}=?\)
1. \(160\)
2. \(16\)
3. \(1.6\)
4. \(0.16\)
Current \(I_1\) through the Zener diode shown in the circuit is:
1. Zero
2. \(0.6\) mA
3. \(0.2\) mA
4. \(0.8\) mA
| 1. | only if both inputs are zero. |
| 2. | if either or both inputs are \(1\). |
| 3. | only if both inputs are \(1\). |
| 4. | if any of the inputs is zero. |
(If diodes are ideal)
| 1. | \(0,0\) | 2. | \(5~\text{mA},5~\text{mA}\) |
| 3. | \(5~\text{mA},0\) | 4. | \(0,5~\text{mA}\) |
The LED:
1. is reverse-biased.
2. is forward-biased.
3. can be made of \(\mathrm{GaAs}\).
4. both (2) & (3) are correct.
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