Physics M.C.Q (1 Marks)

The frequency response curve of RC coupled amplifier is shown in figure. The band width of the amplifier will be

Assertion : NOT gate is also called inverter circuit.
Reason : NOT gate inverts the input order.

Assertion : Zener diode works on a principle of breakdown voltage.
Reason : Current increases suddenly after breakdown voltage.

Assertion : V-i characteristic of P-N junction diode is same as that of any other conductor.
Reason : P-N junction diode behave as conductor at room temperature.

Assertion : Base in a transistor is made very thin as compared to collector and emitter regions.
Reason : Due to thin base power gain and voltage gain is obtained by a transistor.

Assertion : At 0 K Germanium is a superconductor.
Reason : At 0 K Germanium offers zero resistance.

Assertion : NAND or NOR gates are called digital building blocks.
Reason : The repeated use of NAND (or NOR) gates can produce all the basic or complicated gates.

Assertion : A transistor is a voltage-operating device.
Reason : Base current is greater than the collector current.

Assertion : In transistor common emitter mode as an amplifier is preferred over common base mode.
Reason : In common emitter mode the input signal is connected in series with the voltage applied to the base emitter function.

Assertion : Two P-N junction diodes placed back to back, will work as a NPN transistor.
Reason : The P-region of two PN junction diodes back to back will form the base of NPN transistor.

Assertion : Semiconductors do not Obey's Ohm's law.
Reason : Current is determined by the rate of flow of charge carriers.

Assertion : We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals.
Reason : The current through the PN junction is not same in forward and reversed bias.

Assertion : Silicon is preferred over germanium for making semiconductor devices.
Reason : The energy gap for germanium is more than the energy gap of silicon.

Assertion : An N-type semiconductor has a large number of electrons but still it is electrically neutral.
Reason : An N-type semiconductor is obtained by doping an intrinsic semiconductor with a pentavalent impurity.

Assertion : Electron has higher mobility than hole in a semiconductor.
Reason : Mass of electron is less than the mass of hole.

Assertion : The temperature coefficient of resistance is positive for metals and negative for P-type semiconductor.
Reason : The effective charge carriers in metals are negatively charged whereas in P-type semiconductor they are positively charged.

Assertion : If the temperature of a semiconductor is increased then it's resistance decreases.
Reason : The energy gap between conduction band and valence band is very small

Assertion : The resistivity of a semiconductor increases with temperature.
Reason : The atoms of a semiconductor vibrate with larger amplitude at higher temperature there by increasing it's resistivity.

Assertion : A transistor amplifier in common emitter configuration has a low input impedence.
Reason : The base to emitter region is forward biased.

Assertion : In a common emitter transistor amplifier the input current is much less than the output current.
Reason : The common emitter transistor amplifier has very high input impedance.

Assertion : The number of electrons in a P-type silicon semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature.
Reason : It is due to law of mass action.

The output current versus time curve of a rectifier is shown in the figure. The average value of the output current in this case is

Assertion : When PN-junction is forward biased then motion of charge carriers at junction is due to diffusion. In reverse biasing. The cause of motion of charge is drifting.
Reason : In the following circuit emitter is reverse biased and collector is forward biased.

For the diode, the characteristic curves are given at different temperature. The relation between the temperatures is

The mutual characteristic curves of a triode are as shown in figure. The cut off voltage for the triode is

An alternating voltage of 141.4V (rms) is applied to a vacuum diode as shown in the figure. The maximum potential difference across the condenser will be.

The point representing the cut off grid voltage on the mutual characteristic of triode is
 

The given figure shows the wave forms for two inputs A and B and that for the output Y of a logic circuit. The logic circuit is

The output in the circuit of figure is taken across a capacitor. It is as shown in figure

Different voltages are applied across a P-N junction and the currents are measured for each value. Which of the following graphs is obtained between voltage and current 

In a forward biased PN-junction diode, the potential barrier in the depletion region is of the form … 

The temperature (T) dependence of resistivity (r) of a semiconductor is represented by

The voltage gain of the following amplifier is

Amplification factor of a triode is 10. When the plate potential is 200 volt and grid potential is – 4 volt, then the plate current of 4mA is observed. If plate potential is changed to 160 volt and grid potential is kept at – 7 volt, then the plate current will be

Which of the following figures correctly shows the phase relation between the input signal and the output signal of triode amplifier

A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 kilo ohm, is used as an amplifier whose amplification is 10. The resistance connected in plate circuit will be

A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If m = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current

A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be

The plate characteristic curve of a diode in space charge limited region is as shown in the figure. The slope of curve at point P is 5.0 mA/V. The static plate resistance of diode will be

The value of amplification factor from the following graph will be

The mutual characteristic of triode is

A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately

In the following common emitter configuration an NPN transistor with current gain b = 100 is used. The output voltage of the amplifier will be

The variation of anode current in a triode corresponding to a change in grid potential at three different values of the plate potential is shown in the diagram. The mutual conductance of the triode is

In a negative logic the following wave form corresponds to the

The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current

The i-V characteristic of a P-N junction diode is shown below. The approximate dynamic resistance of the P-N junction when a forward bias of 2volt is applied

A source voltage of 8V drives the diode in fig. through a current-limiting resistor of 100 ohm. Then the magnitude of the slope load line on the V-I characteristics of the diode is

The diagram of a logic circuit is given below. The output F of the circuit is represented by

The shows two NAND gates followed by a NOR gate. The system is equivalent to the following logic gate

The curve between charge density and distance near P-N junction will be

The combination of gates shown below produces

A diode is connected to 220 V (rms) ac in series with a capacitor as shown in figure. The voltage across the capacitor is

The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is

A transistor is used as an amplifier in CB mode with a load resistance of 5 k W the current gain of amplifier is 0.98 and the input resistance is 70 W, the voltage gain and power gain respectively are

The peak voltage in the output of a half-wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The dc component of the output voltage is

The grid in a triode valve is used

Current in the circuit will be

In the circuit, if the forward voltage drop for the diode is 0.5V, the current will be

When a potential difference is applied across, the current passing through

Figure gives a system of logic gates. From the study of truth table it can be found that to produce a high output (1) at R, we must have

The following configuration of gate is equivalent to

The typical ionisation energy of a donor in silicon is

The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature

Select the correct statement

Plate voltage of a triode is increased from 200 V to 225 V. To maintain the plate current, change in grid voltage from 5V to 5.75 V is needed. The amplification factor is 

In a diode valve the cathode temperature must be (f = work function)

The ripple factor in a half wave rectifier is

The transconductance of a triode amplifier is 2.5 mili mho having plate resistance of 20 KW, amplification 10. Find the load resistance

The amplification factor of a triode is 50. If the grid potential is decreased by 0.20 V, what increase in plate potential will keep the plate current unchanged

The thermionic emission of electron is due to

The voltage gain of a triode depends upon

The electrical circuits used to get smooth d.c. output from a rectifier circuit is called

For a given triode μ = 20. The load resistance is 1.5 times the anode resistance. The maximum gain will be

Diode is used as a/an

Plate resistance of two triode valves is 2 KW and 4 KW, amplification factor of each of the valves is 40. The ratio of voltage amplification, when used with 4 KW load resistance, will be

In a diode valve, the state of saturation can be obtained easily by

When plate voltage in diode valve is increased from 100 volt to 150 volt then plate current increases from 7.5 mA to 12 mA. The dynamic plastic resistance will be

A 2V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is

Which one is correct relation for thermionic emission
 

Correct relation for triode is
 

Coating of strontium oxide on Tungsten cathode in a valve is good for thermionic emission because

The value of plate current in the given circuit diagram will be

The introduction of a grid in a triode valve affects plate current by

With a change of load resistance of a triode, used as an amplifier, from 50 kilo ohms to 100 kilo ohms, its voltage amplification changes from 25 to 30. Plate resistance of the triode is

The unit of mutual conductance of a triode valve is

The triode constant is out of the following

If the amplification factor of a triode (m) is 22 and its plate resistance is 6600 ohm, then the mutual conductance of this valve is mho is

In the circuit of a triode valve, there is no change in the plate current, when the plate potential is increased from 200 volt to 220 volt and the grid potential is decreased from – 0.5 volt to –1.3 volt. The amplification factor of this valve is

The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 volt the change in plate voltage in order to keep the plate current constant (in volt) is

In a triode valve

The combination of the gates shown in the figure below produces

To get an output 1 from the circuit shown in the figure, the input must be

In a triode amplifier, the value of maximum gain is equal to

In an experiment, the saturation in the plate current in a diode is observed at 240V. But a student still wants to increase the plate current. It can be done, if

The amplification produced by a triode is due to the action of

The amplification factor of a triode is 20. If the grid potential is reduced by 0.2 volt then to keep the plate current constant its plate voltage is to be increased by

For a given plate-voltage, the plate current in a triode is maximum when the potential of

Number of secondary electrons emitted per number of primary electrons depends on

Which of the following logic gate is an universal gate

Which gates is represented by this figure

The output of OR gate is 1

Which logic gate is represented by the following combination of logic gates

A gate in which all the inputs must be low to get a high output is called

The output of a NAND gate is 0

In the CB mode of a transistor, when the collector voltage is changed by 0.5 volt. The collector current changes by 0.05 mA. The output resistance will be

Which logic gate is represented by following diagram

This symbol represents

The Boolean equation of NOR gate is

If A and B are two inputs in AND gate, then AND gate has an output of 1 when the values of A and B are

The given truth table is of

Which represents NAND gate 
 

Which of the following gates will have an output of 1(a)

How many NAND gates are used to form an AND gate
 

A gate has the following truth table The gate is

A logic gate is an electronic circuit which

The logic behind ‘NOR’ gate is that it gives

Boolean algebra is essentially based on

The truth table shown in figure is for

Given below are four logic gate symbol (figure). Those for OR, NOR and NAND are respectively

In a transistor in CE configuration, the ratio of power gain to voltage gain is

NPN transistor are preferred to PNP transistor because they have

In NPN transistor the collector current is 10 mA. If 90% of electrons emitted reach the collector, then

Consider an NPN transistor amplifier in common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current

Which of the following is used to produce radio waves of constant amplitude

When NPN transistor is used as an amplifier

Which of these is unipolar transistor

In a transistor configuration b-parameter is

In a transistor, a change of 8.0 mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce the same change in the collector current

In case of NPN-transistors the collector current is always less than the emitter current because

In a common base amplifier circuit, calculate the change in base current if that in the emitter current is 2 mA and a = 0.98

For a transistor, the current amplification factor is 0.8. The transistor is connected in common emitter configuration. The change in the collector current when the base current changes by 6 mA is

The part of a transistor which is heavily doped to produce a large number of majority carriers, is

For the given combination of gates, if the logic states of inputs A, B, C are as follows A = B = C = 0 and A = B = 1, C = 0 then the logic states of output D are

An NPN-transistor circuit is arranged as shown in figure. It is

The most commonly used material for making transistor is

The combination of ‘NAND’ gates shown here under (figure) are equivalent to

The symbol given in figure represents

A common emitter amplifier is designed with NPN transistor (a = 0.99). The input impedance is 1 KW and load is 10 KW. The voltage gain will be

Given below are symbols for some logic gates

The XOR gate and NOR gate respectively are

In a PNP transistor the base is the N-region. Its width relative to the P-region is

A transistor is used in common emitter mode as an amplifier. Then

For a transistor the parameter b = 99. The value of the parameter a is

The transfer ratio of a transistor is 50. The input resistance of the transistor when used in the common-emitter configuration is 1 KW. The peak value for an A.C input voltage of 0.01 V peak is

The transistors provide good power amplification when they are used in

Least doped region in a transistor

In a common emitter transistor, the current gain is 80. What is the change in collector current, when the change in base current is 250 mA

Symbolic representation of photodiode is
 

In P-N junction, the barrier potential offers resistance to

A semiconductor X is made by doping a germanium crystal with arsenic (Z = 33). A second semiconductor Y is made by doping germanium with indium (Z = 49). The two are joined end to end and connected to a battery as shown. Which of the following statements is correct

The width of forbidden gap in silicon crystal is 1.1 eV. When the crystal is converted in to a N-type semiconductor the distance of Fermi level from conduction band is

Zener diode is used as

In a PNP transistor working as a common-base amplifier, current gain is 0.96 and emitter current is 7.2 mA. The base current is

Which of the following is true

In the case of constants a and b of a transistor

A NPN transistor conducts when

In an NPN transistor the collector current is 24 mA. If 80% of electrons reach collector its base current in mA is

The emitter-base junction of a transistor is …… biased while the collector-base junction is ……. biased

An oscillator is nothing but an amplifier with

When NPN transistor is used as an amplifier

In a full wave rectifiers, input ac current has a frequency ‘n’. The output frequency of current is

If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be

The current through an ideal PN-junction shown in the following circuit diagram will be

In the diagram, the input is across the terminals A and C and the output is across the terminals B and D, then the output is

Which is the wrong statement in following sentences? A device in which P and N-type semiconductors are used is more useful then a vacuum type because

To make a PN junction conducting

If no external voltage is applied across P-N junction, there would be

No bias is applied to a P-N junction, then the current

Which one of the following statements is not correct

The correct symbol for zener diode is