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MCQOPTIONS
This section includes 1017 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 901. |
The turn off time of a bipolar transistor is about |
| A. | 0.5 ns |
| B. | 10 ns |
| C. | 70 ns |
| D. | 150 ns |
| Answer» D. 150 ns | |
| 902. |
The kinetic energy of free electrons in a metal is (where k is the de-Broglie wave number of the electron) |
| A. | inversely proportional to k |
| B. | inversely proportional to square of k |
| C. | proportional to k |
| D. | proportional to the square of k |
| Answer» C. proportional to k | |
| 903. |
A silicon (PN) junction at a temperature of 20°C has a reverse saturation current of 10 pico Ampere. The reverse saturation current at 40°C for the same bias is approximately. |
| A. | 30 pA |
| B. | 40 pA |
| C. | 50 pA |
| D. | 60 pA |
| Answer» C. 50 pA | |
| 904. |
The derating factor for a BJT transistor is about |
| A. | 0.5 mW/°C |
| B. | 2.5 mW/°C |
| C. | 10 mW/°C |
| D. | 25 mW/°C |
| Answer» C. 10 mW/¬∞C | |
| 905. |
Which variety of copper has the best conductivity? |
| A. | Pure annealed copper |
| B. | Hard drawn copper |
| C. | Induction hardened copper |
| D. | Copper containing traces of silicon |
| Answer» B. Hard drawn copper | |
| 906. |
The circuit shown in the figure is best described as a |
| A. | bridge rectifier |
| B. | ring modulator |
| C. | frequency discriminator |
| D. | voltage doubler |
| Answer» E. | |
| 907. |
In an n-p-n transistor biased for operation in forward active region |
| A. | emitter is positive with respect to base |
| B. | collector is positive with respect to base |
| C. | base is positive with respect to emitter and collector is positive with respect to base |
| D. | none of the above |
| Answer» D. none of the above | |
| 908. |
The cut in voltage |
| A. | is the same for silicon and germanium diodes |
| B. | is a forward voltage |
| C. | is a reverse voltage |
| D. | is a forward voltage below which the current is very small |
| Answer» E. | |
| 909. |
Which of the following is the ferric electric material? |
| A. | Rochelle salt |
| B. | Barium titanate |
| C. | Potassium dihydrogen phosphate |
| D. | All of the above |
| Answer» E. | |
| 910. |
The equivalent circuit of an ideal diode is |
| A. | a charging condenser |
| B. | a discharging condenser |
| C. | a switch |
| D. | a resistor |
| Answer» D. a resistor | |
| 911. |
Fermi level in intrinsic semiconductor is at the centre of forbidden energy band. |
| A. | 1 |
| B. | |
| C. | emitter base junction |
| D. | collector base junction |
| Answer» B. | |
| 912. |
Which of the following materials has the highest electrical conductivity? |
| A. | Steel |
| B. | Silver |
| C. | Aluminium |
| D. | Zinc |
| Answer» C. Aluminium | |
| 913. |
Before doping the semiconductor material is |
| A. | dehydrated |
| B. | heated |
| C. | hardened |
| D. | purified |
| Answer» E. | |
| 914. |
Assertion (A): The forward resistance of a p-n diode is not constant. Reason (R): The v-i characteristics of p-n diode is non-linear. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not a correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not a correct explanation of A | |
| 915. |
Which materials find application in MASER? |
| A. | Diamagnetic |
| B. | Paramagnetic |
| C. | Ferromagnetic |
| D. | Ferrimagnetic |
| Answer» B. Paramagnetic | |
| 916. |
An amplifier without feedback has a voltage gain of 50, input resistance of 1 kΩ and output resistance of 2.5 kΩ. The input resistance of the current shunt -ve feedback amplifier using the above amplifier with a feedback factor of 0.2 is |
| A. | 1/11 kΩ |
| B. | 1/5 kΩ |
| C. | 5 kW |
| D. | 11 kW |
| Answer» B. 1/5 kŒ© | |
| 917. |
The number of doped regions in PIN diode is |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 1 or 2 |
| Answer» C. 3 | |
| 918. |
In a JFET, the drain current is maximum when |
| A. | VGS = 0 |
| B. | VGS is not zero but is slightly negative |
| C. | VGS is negative |
| D. | VGS is negative and equal to VDS |
| Answer» B. VGS is not zero but is slightly negative | |
| 919. |
From an n channel JFET for VDS constant and if VGS is made more negative, pinch off would occur at |
| A. | higher value of drain current |
| B. | saturation value of drain current |
| C. | zero drain current |
| D. | gate current equal to drain current |
| Answer» D. gate current equal to drain current | |
| 920. |
In which of the following does a negative resistance region exist in the v-i characteristics? |
| A. | PIN diode |
| B. | Schottky diode |
| C. | Tunnel diode |
| D. | Zener diode |
| Answer» D. Zener diode | |
| 921. |
The early effect in a BJT is caused by |
| A. | fast turn on |
| B. | fast turn off |
| C. | large collector base reverse bias |
| D. | large emitter base forward bias |
| Answer» D. large emitter base forward bias | |
| 922. |
Calculate the resistivity of n-type semiconductor from the following data, Density of holes = 5 x 1012 cm-3. Density of electrons = 8 x 1013 cm-3, mobility of conduction electron = 2.3 x 104 cm2/ V-sec and mobility of holes = 100 cm2/V-sec. |
| A. | 0.43 Ω-m |
| B. | 0.34 Ω-m |
| C. | 0.42 Ω-m |
| D. | 0.24 Ω-m |
| Answer» C. 0.42 Œ©-m | |
| 923. |
The current through a PN Junction diode with v volts applied to the P region to the N region, where (I0 is the reverse saturation current to the diode, m the ideality factor, k the Boltzmann constant, T the absolute temperature and q the magnitude of charge on an electron) is |
| A. | I0 (e-qv/mkT - 1) |
| B. | I0 e-qv/mkT |
| C. | I0 (1 - eqv/mkT) |
| D. | I0 (eqv/mkT - 1) |
| Answer» C. I0 (1 - eqv/mkT) | |
| 924. |
Typical value of reverse current in a semiconductor diode is |
| A. | 0.041666666666667 |
| B. | 0.1 A |
| C. | 1 μA |
| D. | 0.1 μA |
| Answer» E. | |
| 925. |
Assertion (A): When a photoconductive device is exposed to light, its bulk resistance increases. Reason (R): When exposed to light, electron hole pairs are generated in the photoconductive device. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not a correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» E. | |
| 926. |
As per Einstein's equation, the velocity of emitted electron in photoelectric emission is given by the equation |
| A. | mv2 = hf - Uw |
| B. | mv2 ≤ hf - Uw |
| C. | mv2 = hf + Uw |
| D. | mv2 ≤ hf + Uw |
| Answer» C. mv2 = hf + Uw | |
| 927. |
How many free electrons does a p type semiconductor has? |
| A. | only those produced by thermal energy |
| B. | only those produced by doping |
| C. | those produced by doping as well as thermal energy |
| D. | any of the above |
| Answer» B. only those produced by doping | |
| 928. |
Assertion (A): When light falls at junction of p-n photodiode, its p side becomes positive and n side becomes negative. Reason (R): When a photodiode is short circuited, the current in the external circuit flows from p side to n side. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not a correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not a correct explanation of A | |
| 929. |
An intrinsic semiconductor (intrinsic electron density = 1016 m-3) is deped with donors to a level of 1022 m-3. What is the hole density assuming all donors to be ionized? |
| A. | 107 m-3 |
| B. | 108 m-3 |
| C. | 1010 m-3 |
| D. | 106 m-3 |
| Answer» E. | |
| 930. |
SCR turns of from conducting state to blocking state on |
| A. | reducing gate current |
| B. | reversing gate voltage |
| C. | reducing anode current below holding current value |
| D. | applying ac to the gate |
| Answer» D. applying ac to the gate | |
| 931. |
In which of the following is the width of junction barrier very small? |
| A. | Tunnel diode |
| B. | Photo diode |
| C. | PIN diode |
| D. | Schottky diode |
| Answer» E. | |
| 932. |
In a bipolar transistor the barrier potential |
| A. | 0 |
| B. | a total of 0.7 V |
| C. | 0.7 V across each depletion layer |
| D. | 0.35 V |
| Answer» D. 0.35 V | |
| 933. |
Fermi level is the maximum energy that an electron can possess at 0 K. |
| A. | 1 |
| B. | |
| C. | 100 V |
| D. | 50 V |
| Answer» B. | |
| 934. |
A sample of N-type semiconductor has electron density of 6.25 x 1018/cm3 at 300k. If the intrinsic concentration of carriers in this sample is 2.5 x 1013/cm3 at this temperature the hole density works out to be |
| A. | 106/cm3 |
| B. | 108/cm3 |
| C. | 1010/cm3 |
| D. | 10l2/cm3 |
| Answer» C. 1010/cm3 | |
| 935. |
The maximum power handling capacity of a resistor depends on |
| A. | total surface area |
| B. | resistance value |
| C. | thermal capacity of the resistor |
| D. | resistivity of the material used in the resistor |
| Answer» D. resistivity of the material used in the resistor | |
| 936. |
Which of these has a layer of intrinsic semiconductor? |
| A. | Zener diode |
| B. | PIN diode |
| C. | Photo diode |
| D. | Schottky diode |
| Answer» C. Photo diode | |
| 937. |
In a bipolar transistor, the base collector junction has |
| A. | forward bias |
| B. | reverse bias |
| C. | zero bias |
| D. | zero or forward bias |
| Answer» C. zero bias | |
| 938. |
Consider the following statement S1 and S2. S1: The β of a bipolar transistor reduces if the base width is increased. S2: the β of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct? |
| A. | S1 is False, S2 is true |
| B. | S1 and S2 both are true |
| C. | S1 and S2 both are false |
| D. | S1 is true, S2 is false |
| Answer» E. | |
| 939. |
A semiconductor diode is biased in forward direction and carrying current I. The current due to holes in p material is |
| A. | I |
| B. | 0 |
| C. | less than I |
| D. | 0.5 |
| Answer» D. 0.5 | |
| 940. |
When P-N junction is in forward bias, by increasing the battery voltage |
| A. | current through P-N junction reduces |
| B. | current through P-N junction increases |
| C. | circuit resistance increases |
| D. | none of the above |
| Answer» C. circuit resistance increases | |
| 941. |
The types of carriers in a semiconductor are |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 942. |
For BJT transistor. The maximum power dissipation is specified as 350 mW if ambient temperature is 25°C. If ambient temperature is 60°C the maximum power dissipation should be limited to about |
| A. | 100 mW |
| B. | 250 mW |
| C. | 450 mW |
| D. | 600 mW |
| Answer» C. 450 mW | |
| 943. |
It is required to trace the output characteristics of a CE bipolar transistor on a CRO screen. The proper method is |
| A. | apply the voltage drop across collector resistance to Y input, disconnect sweep generator and apply VCE to X input |
| B. | apply voltage drop across collector resistance to Y input |
| C. | apply VCE to X input |
| D. | apply VCE to Y input, disconnect the sweep generator and apply voltage drop across collector resistance to X input |
| Answer» B. apply voltage drop across collector resistance to Y input | |
| 944. |
In a bipolar transistor which current is largest |
| A. | collector current |
| B. | base current |
| C. | emitter current |
| D. | base current or emitter current |
| Answer» D. base current or emitter current | |
| 945. |
Pentavalent impurity creates n type semiconductor. |
| A. | 1 |
| B. | |
| C. | both junctions are forward biased |
| D. | both junctions are reverse biased |
| Answer» B. | |
| 946. |
Assertion (A): In active region of CE output characteristics of BJT, collector current is nearly constant. Reason (R): Base current in CE connection is very small. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not a correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not a correct explanation of A | |
| 947. |
For generating 1 MHz frequency signal, the most suitable circuit is |
| A. | phase shift oscillator |
| B. | weinbridge oscillator |
| C. | colpitt's oscillator |
| D. | clapp oscillator |
| Answer» D. clapp oscillator | |
| 948. |
AE 139 is a |
| A. | tunnel diode |
| B. | germanium power transistor |
| C. | photoconductive cell |
| D. | silicon diode |
| Answer» C. photoconductive cell | |
| 949. |
In a degenerate n type semiconductor material, the Fermi level, |
| A. | is in valence band |
| B. | is in conduction band |
| C. | is at the centre in between valence and conduction bands |
| D. | is very near valence band |
| Answer» C. is at the centre in between valence and conduction bands | |
| 950. |
When a p-n junction is forward biased. The width of depletion layer decreases. |
| A. | 1 |
| B. | |
| Answer» B. | |