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Right choice is (a) TRUE

Easy explanation: Yes, this is a true statement. The BASE is the middle section of the transistor that forms two p-n junctions with the EMITTER and the collector. It is very thin and lightly doped so as to pass most of the emitter INJECTED CHARGE carriers to the collector.

The correct CHOICE is (a) The emitter-base junction is forward biased and the base-collector junction is REVERSE biased

Easiest explanation: In order to use a transistor as an amplifier the emitter-base junction is set up as forward biased and the base-collector junction is set up as reverse biased. This is the criteria for MAKING a transistor FUNCTION as an amplifier.

The correct choice is (c) INSULATORS

Easiest explanation: The BANDGAP is maximum in insulators. This makes it difficult for electrons to move to the conduction band. This is contrary to metals and superconductors, which has MINIMUM band gaps facilitating the MOVEMENT of electrons.

Correct answer is (d) 90

Explanation: The expression of VOLTAGE GAIN is as follows:

AV=\(\frac {αR_L}{R_e}\)

GIVEN: α = 0.90, RL = 5.0 kΩ = 5000 Ω, Re = 50 Ω

AV=\(\frac {0.90×5000}{50}\)

AV = 90

Correct OPTION is (a) 2

To explain I WOULD say: A transistor has three doped regions forming two p-n junctions between them. There are two TYPES of TRANSISTORS, namely n-p-n transistors and p-n-p transistors. In n-p-n transistors, the two segments of the n-type semiconductor are separated by a segment of p-type semiconductor, and in a p-n-p transistor, it’s just the opposite scenario.

Correct answer is (b) Solar cell

To elaborate: Solar cells CONVERT solar energy into electric energy. A solar cell is a p-n junction that generates emf when solar radiation FALLS on the p-n junction. It works on the same principle as the photodiode, EXCEPT that no external bias is APPLIED and the junction area is kept large.

The correct answer is (a) 1.11

The best EXPLANATION: For a full-wave RECTIFIER,

Irms=\(\FRAC {I_m}{\sqrt {2}}\); Idc=\(\frac {2I_m}{\pi}\)

Form factor=\(\frac {I_{RMS}}{I_{dc}}\)

Form factor=\(\frac {\frac {I_m}{\sqrt {2}}} {\frac {2I_m}{\pi}}\)

Form factor=\(\frac {\pi }{2\sqrt {2}}\)=1.11

The correct ANSWER is (d) Electrons

The best I can explain: In n-type semiconductors, electrons are majority charge carriers. It is made by adding an IMPURITY to a pure semiconductor. This is the opposite SCENARIO of p-type semiconductors where electrons are the minority charge carriers.

Right CHOICE is (b) The depletion region is increased

For explanation I would say: When a p-n diode is reverse biased, its depletion region is widened. This is because the voltage at the CATHODE will be HIGHER than at the anode. This has the effect of increasing or DECREASING the EFFECTIVE resistance of the junction itself allowing or blocking current flow through the diode.

Right option is (a) The valence band is partially FILLED with ELECTRONS

The best explanation: In insulators, the conduction band is empty and the valence band is filled with electrons. The other OPTIONS do not CORRESPOND to the concept of insulators, but rather conductors and semiconductors.

Correct answer is (a) True

For explanation I WOULD say: Yes, this is a true statement. In COMPARISON with the sizes of all the other devices that are used in Integrated Circuits, inductors are FAIRLY huge. Making small inductors with DESIRED CHARACTERISTICS is very expensive, therefore, designers try not to use inductors in Integrated circuits.

Right choice is (b) Solar cell

Easiest explanation: Zener diode was INVENTED by Clarence Melvin Zener. It is designed to OPERATE under reverse BIAS in the BREAKDOWN region and is used as a voltage regulator. It is designed to allow current to flow BACKWARD.

The correct ANSWER is (d) 0.065 A

For explanation: Given: I0 = 0.092 A

The required equation is ➔ IRMS = \(\frac {I_O}{\SQRT {2}}\)

Irms = \(\frac {0.092}{1.414}\)

Irms = 0.065 A

Correct choice is (C) Insulator

The explanation: At absolute zero, the element, silicon (Si) acts as an insulator due to the absence of FREE electrons in the conduction BAND. The other OPTIONS are not valid.

The correct CHOICE is (b) False

Explanation: No, this statement is false. When a strong CURRENT is passed through a semiconductor, this CAUSES many covalent bonds to break up due to heating and THEREBY to liberate a large NUMBER of free electrons.

The correct CHOICE is (b) Charge CARRIERS density

The EXPLANATION: Drift current is due to the high concentration of holes in the p-region and the high concentration of electrons in the n-region of the junction diode. The combined effect of the MOVEMENT of minority charge carriers results in drift current.

Right answer is (a) True

Best explanation: Yes, this is a true STATEMENT. The truth table is a table that shows all possible input combinations and the CORRESPONDING output combinations for a PARTICULAR logic gate. These are USED in connection with Boolean algebra, Boolean FUNCTIONS, and propositional calculus.

The CORRECT option is (C) Drift of charges

Explanation: The reverse current is mainly due to the drift of charges. It is due to the carriers like HOLES and free electrons passing through a square centimeter area that is perpendicular to the direction of flow.

Right answer is (c) High

Easy explanation: When a p-n diode is reverse BIASED, it OFFERS high RESISTANCE. Forward biasing of p-n junction diode offers low resistance. In the case of an ideal p-n junction, resistance is ZERO. So, the OHMMETER can measure zero resistance.

The correct answer is (a) Ions

Easiest EXPLANATION: The potential barrier in the depletion layer is due to the presence of immobile ions. The acceptor and DONOR atoms will gain negative and POSITIVE CHARGES leading to p-n JUNCTION formation. Hence, acceptor and donor are immobile ions.

Right CHOICE is (a) Gallium

Best explanation: SUBSTANCES such as gallium, boron, and aluminum are all trivalent atoms. These are called acceptor impurities and they PRODUCE p-type semiconductors. Therefore, germanium is doped with gallium in a p-type semiconductor.

Right answer is (c) The resistivity of a semiconductor increases with INCREASE in temperature

The BEST explanation: Resistivity of a semiconductor and temperature are inversely PROPORTIONAL to each other. When the resistivity of a semiconductor decreases, the temperature increases. Semiconductors have BULK resistivity in the range of 10^3-ohm cm.

Correct choice is (d) η=\(\frac {dc \, power \, DELIVERED \, to \, LOAD}{ac \, input \, power \, from \, transformer \, SECONDARY}\)

Easy explanation: The RECTIFICATION efficiency tells us what percentage of the total input ac power can be converted into useful dc output power. The expression for rectification efficiency is GIVEN as:

η=\(\frac {dc \, power \, delivered \, to \, load}{ac \, input \, power \, from \, transformer \, secondary}\)

The correct option is (B) Regulator

The best explanation: Zener diode can be used as a voltage regulator. They can also be used as shunt REGULATORS to regulate the voltage across small circuits. Zener DIODES are always OPERATED in a reverse-biased condition.

Correct option is (a) The high POTENTIAL at n-side and low potential at p-side

The EXPLANATION: In an UNBIASED p-n junction, the high potential is at the n-side and the low potential at the p-side. When the polarity of the battery is REVERSED, the p-n junction gets reverse biased and does not conduct electric CURRENT.

Right option is (c) Intrinsic semiconductor

Best explanation: Pure SEMICONDUCTORS are called intrinsic semiconductors. The number of ELECTRONS in the CONDUCTION band will be equal to the number of holes in the valence band. Intrinsic semiconductors are the semiconductors which are not doped with any IMPURITIES.