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Quizzes

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Exam:
1821 quizzes
A transistor has a ratio α = 0.975 of the collector current to the emitter current. What is its current gain β in the common-emitter circuit? New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A transistor works as a switch with the load in the collector lead. A student applies a high voltage to the base through a resistor, so that the base current is more than the least current for saturation. What does she find at the output, taken across the transistor from the collector to the emitter? New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A student builds a pre-amplifier for a small sensor with one transistor of current gain 75. The load in the collector lead is 2.7 kΩ, and she measures an input resistance of 650 Ω at the base. By what factor does the circuit multiply a small signal voltage? Give the size only. New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
The two inputs of a NOR gate are joined together, and one signal A is applied to both. A student writes the truth table of the output for A = 0 and for A = 1. Which behaviour does she find? New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
Two signals of four bits each are applied to the two inputs of an XOR gate. The input A is 1010 and the input B is 1100, read from left to right. What is the output, bit by bit? New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A student says that the base plays a small part in a transistor. She argues that the base current is only about one per cent of the collector current. She adds that the collector current would be nearly the same if the base wire were cut. Which reply is correct? New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A burglar alarm uses a buzzer of 250 Ω that is fed from a 10 V battery through a transistor of current gain 125. When the alarm rings, the transistor is saturated and keeps 0.2 V between its collector and emitter. How small can the base current be while the alarm still rings at full strength? New
High School (11–12) · Transistors and Logic Gates
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A student measures the resistance of a thermistor made of a semiconductor and of a copper wire, first in a cold bath and then in a warm bath. How do the two resistances change when the bath is warmed? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
Silicon is doped with donors, 4.0 × 10²⁰ in each cubic metre. At room temperature ni = 1.0 × 10¹⁶ m⁻³. Assume that every donor gives one electron. How many holes are there in each cubic metre? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A p-n junction is connected to a battery with the positive terminal on the p side. Compare the junction with the same junction when it is not connected. What happens to the depletion layer and to the barrier? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A small lamp of fixed resistance 260 Ω is in a loop with a cell of 6.4 V and a germanium diode. The diode is connected so that it conducts, and it drops 0.3 V. How much current does the lamp carry? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A student says: in the depletion layer of an unbiased p-n junction there are no charges at all, so there is no electric field in it. Which reply is correct? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A forward-biased silicon diode carries 4.0 mA. Take VT = 26 mV, and the ideality factor 1. What is the dynamic resistance of the diode at this current? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
The reverse current of a silicon diode is a few nanoampere at 300 K. A designer warms the diode to a higher temperature with the reverse voltage kept fixed. How does the reverse current change, and why? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A battery charger uses a half-wave rectifier with an ideal diode. The transformer gives a peak voltage of 24 V. What is the mean (direct) voltage of the output? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
In a Zener regulator, the input voltage rises a little and the load resistor stays the same. The Zener diode is working in breakdown. Which statement describes what happens? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A small radio is powered from the 50 Hz mains through a bridge rectifier. A reservoir capacitor of 1500 µF stands across the radio, which draws 81 mA. By how much does the voltage across the capacitor sag between one charging peak and the next? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
An indicator lamp on a panel is one LED, which glows well at 20 mA. When it conducts, there is 2.7 V across it. The panel has a 15 V line. What resistor in series with the LED sets the current at its working value? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+17
StemPy LabStemPy Lab
Medium
A student joins a 4.1 V Zener diode directly across a 12 V battery, in reverse bias, with no series resistor. The battery has a very small internal resistance. What happens? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A caravan carries a flat panel of 0.45 m² on its roof. On a hazy day the sunlight that reaches the roof is 750 W/m², and the panel turns 17 % of the light power into electrical power. How many watt does the panel give? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
A photodiode and a solar cell are both p-n junctions that are lit by light. One is used with a reverse bias and the other with no bias. Which pair describes the reason correctly? New
High School (11–12) · Semiconductors and Diodes
AEEE (Amrita)AMUEEEAP EAPCET+22
StemPy LabStemPy Lab
Hard
Electron scattering gives a radius of 3.3 fm for a nucleus with 20 nucleons. A physicist wants to predict the size of a heavier nucleus with 160 nucleons from this one measurement. What radius should she expect? New
High School (11–12) · Nuclei and Radioactivity
APA-LevelIB+20APA-LevelIB
StemPy LabStemPy Lab
Medium
Nucleus X has the mass number 12 and nucleus Y has the mass number 208. Compared with X, nucleus Y has New
High School (11–12) · Nuclei and Radioactivity
APA-LevelIB+20APA-LevelIB
StemPy LabStemPy Lab
Medium
The atomic mass of lithium-7 is 7.016004 u. Use mH = 1.007825 u, mn = 1.008665 u and 1 u = 931.494 MeV/c². What is its binding energy? New
High School (11–12) · Nuclei and Radioactivity
APA-LevelIB+20APA-LevelIB
StemPy LabStemPy Lab
Medium
Tritium has a binding energy of 8.48 MeV and helium-3 has 7.72 MeV. Each has three nucleons. Which statement is correct? New
High School (11–12) · Nuclei and Radioactivity
APA-LevelIB+20APA-LevelIB
StemPy LabStemPy Lab
Medium
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