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151.

The correct relation between current gains `alpha` and `beta` isA. `beta =(alpha)/(1 -alpha)`B. `beta =(alpha)/(1+alpha)`C. `beta =alpha(1-alpha)`D. `beta = (1-alpha)/(alpha)`

Answer» Correct Answer - A
152.

Transistors are made of.A. insulatorsB. conductorsC. alloysD. doped semi-conductors

Answer» Correct Answer - D
153.

In `n-p-n` transistor the arrow head on emitter represents that the convantional current flows fromA. base to emitterB. emitter to baseC. emitter to collectorD. base to collector

Answer» Correct Answer - A
154.

In transistor the emitter current is.A. slightly more than the collector currentB. slightly less than the collector currentC. equal to the collector currentD. equal to the base current

Answer» Correct Answer - A
155.

In the use of transistor as an amplifierA. the emitter - base junction is revrese biased and the collector base junction is also revrese biasedB. the emitter - base junction is forward biased and the collector -base junction is reverse biasedC. both the junctions are forward biasedD. any of the two junctions may be forward biased

Answer» Correct Answer - B
156.

One way in which the operation of an `npn` transistor differ from that of a `pnp` transistor is thatA. the emitter junction is reverse biased in `npn`B. the emitter junction injects minority carriers into the base region of the `pnp`.C. the emitter injects holes into the base of the `pnp` and electrons into the base region of `npn`D. the emitter injects holes into the base of `npn`.

Answer» Correct Answer - C
157.

The combination of the gates shown below produces .A. `AND` gateB. `XOR` gateC. `NOR` gateD. `NAND` gate

Answer» Correct Answer - D
The output of `G_(1)` is `overline(A) G_(2)` is `overline(B)`. Hence output of `G_(3)` is `AB :. y = overline(AB)` i.e., `NAND` gate.
158.

The combination of gates shown below yields .A. `NAND` gateB. `OR` gateC. `NOT` gatesD. `XOR` gate

Answer» Correct Answer - B
`X = overline(overline(A). overline(B)) = overline(overline(A))+overline(overline(B)) = A + B`. It is `OR` gate.
159.

The expression of `Y` in following circuit is .A. `ABCD`B. `A+BCD`C. `A+B+C+D`D. `AB+CD`

Answer» Correct Answer - C
`Y_(1)=A+D,Y_(2)=A +D+B`,
`Y =A +D+B+C`.
160.

The output of the combination of the gates shown in the figure below is .A. `A+A.B`B. `(A+B)A+ overline (B)`C. `(A.B)+(overline(A). overline(B))`D. `(A+B)(overline(A.B))`

Answer» Correct Answer - A
The input to `OR` gate is `A` and `A.B`.
Hence
`Y = A + BA`.
161.

Assertion (A) : `Si` and `GaAs` are preferred materials for solar cells Reason (R ) : Energy gap of `Si` is `1.1 eV` and that of `GaAs` is `1.53 eV` which gives maximum irradiance where as other materials like `CdS` or `CdSe (E_(g) = 2.4 eV)` and `PbS (E_(g) = 0.4 eV)` given minimum irradiance.

Answer» Correct Answer - 1
162.

In the Boolean algebra, the following one is wrongA. `1.0=0`B. `0.1 =0`C. `1.1 = 0`D. `1.1 =1`

Answer» Correct Answer - C
163.

In Boolean algebra `A.B = Y` implies that :A. product of `A` and `B` is `Y`B. `Y` exists when `A` exists or `B` existsC. `Y` exists when both `A` and `B` exist but not when only `A` or `B` existsD. `Y` exists when `A` or `B` exists but not both `A` and `B` exist.

Answer» Correct Answer - C
164.

A three terminal device with one terminal common to both the output and input is called.A. rectifierB. transistorC. diodeD. triode

Answer» Correct Answer - B
165.

Boolean algebra is essentially based onA. symbolsB. logicC. truthD. numbers

Answer» Correct Answer - B
166.

The gate that has only one input terminalA. `NOT`B. `NOR`C. `NAND`D. `XOR`

Answer» Correct Answer - A
167.

Among the following one gives output `1` in the `AND` gate.A. `A = 0,B=0`B. `A=1,B=1`C. `A=1,B=0`D. `A =0,B=1`

Answer» Correct Answer - B
168.

Consider a two-input `AND` gate of figure below. Out of the four entries for the Truth Table given here, the correct ones are. .A. AllB. `1` and `2` onlyC. `1,2` and `3` onlyD. `1,3` and `4` only

Answer» Correct Answer - C
Cheack the truth table.
169.

The output of a 2-input `OR` gate is zero only when itsA. both inputs are `0`B. either input is `1`C. both inputs are `1`D. either input is zero

Answer» Correct Answer - A
170.

Justify the output wavefrom (y) of the OR gate for input and as gives in Fig.

Answer» Note the following :
`{:(At,t lt t_(1),,A=0,B=0 ,,HenceY=0),("For",t_(1)"to" t_(2),,A =1,B=0 ,,Hence Y=1),("For",t_(2)"to" t_(3) ,,A =1,B=1,,Hence Y=1),("For",t_(3) "to" t_(4),,A=0,B=1,,Hence Y=1),("For",t_(4)"to" t_(5) ,,A =0,B=0 ,,Hence Y=0),("For",t_(5) "to" t_(6),,A =1,B=0,,Hence Y=1),("For",t gt t_(6) ,,A =0,B=1,,Hence Y=1):}`
Therefore the wave from `Y` will be as shown in the Fig.