Physics M.C.Q (1 Marks)

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

(a)

(b) 25

(c)

(d)

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

(a) 15

(b) 20

(c) 25

(d) 35

 electrons reach the anode per second. If the power consumed is 448 milliwatts, then the plate (anode) voltage is

(a) 150 V

(b) 200V

(c) 14 × 448 V

(d) 448/14V

The slope of plate characteristic of a vacuum tube diode for certain operating point on the curve is   The plate resistance of the diode and its nature respectively

(a) 100 kilo-ohms static	(b) 1000 kilo-ohms static
(c) 1000 kilo-ohms dynamic	(d) 100 kilo-ohms dynamic

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

(a) 0.02

(b) 0.002

(c) 4.5

(d) 5.0

In a triode valve

(a) If the grid voltage is zero then plate current will be zero

(b) If the temperature of filament is doubled, then the thermionic current will also be doubled

(c) If the temperature of filament is doubled, then the thermionic current will nearly be four times

(d) At a definite grid voltage the plate current varies with plate voltage according to Ohm’s law

The combination of the gates shown in the figure below produces

(a) NOR gate

(b) OR gate

(c) AND gate

(d) XOR gate

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

(a) A = 0, B = 1, C = 0

(b) A = 1, B = 0,  C = 0

(c) A = 1, B = 0, C = 1

(d) A = 1, B = 1, C = 0

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

(a) Half the amplification factor	(b) Amplification factor
(c) Twice the amplification factor	(d) Infinity

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

(a) The plate voltage is increased further

(b) The plate voltage is decreased

(c) The filament current is decreased

(d) The filament current is increased

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

(a) Filament

(b) Cathode

(c) Grid

(d) Plate

For a triode   kilo ohm and  milli mho. If the load resistance is double of plate resistance, then the value of voltage gain will be

(a) 10

(b) 20

(c) 15

(d) 30

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

(a) 10 volt

(b) 4 volt

(c) 40 volt

(d) 100 volt

In a triode amplifier,  kilo ohm and load resistance   kilo ohm. If the input signal voltage is 0.5 volt, then output signal voltage will be

(a) 1.25 volt

(b) 5 volt

(c) 2.5 volt

(d) 10 volt

The amplification factor of a triode is 20 and trans-conductance is 3 milli mho and load resistance 3   then the voltage gain is

(a) 16.36

(b) 28

(c) 78

(d) 108

Following is the relation between current and charge   then value of V_L will be

(a)

(b)

(c)

(d)

In an amplifier the load resistance   is equal to the plate resistance (. The voltage amplification is equal to

(a) μ

(b) 2 μ

(c) μ/2

(d) μ/4

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

(a) Material of target	(b) Frequency of primary electrons
(c) Intensity	(d) None of the above

Thermionic emission from a heated filament varies with its temperature T as

(a)

(b) T

(c)

(d)

Which of the following logic gate is an universal gate

(a) OR

(b) NOT

(c) AND

(d) NOR

Sum of the two binary numbers  and    is

(a)

(b)

(c)

(d)

The output of OR gate is 1

(a) If both inputs are zero	(b) If either or both inputs are 1
(c) Only if both input are 1	(d) If either input is zero

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

(a) OR

(b) NAND

(c) AND

(d) NOR

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

(a) A NAND gate

(b) An inverter

(c) A NOR gate

(d) An AND gate

The output of a NAND gate is 0

(a) If both inputs are 0

(b) If one input is 0 and the other input is 1

(c) If both inputs are 1

(d) Either if both inputs are 1 or if one of the inputs is 1 and the other 0

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

(a) A = 0, B = 0

(b) A = 1, B = 1

(c) A = 1, B = 0

(d) A = 0, B = 1

The given truth table is of

(a) OR gate

(b) AND gate

(c) NOT gate

(d) None of above

How many NAND gates are used to form an AND gate

(a) 1

(b) 2

(c) 3

(d) 4

A gate has the following truth table

The gate is

(a) NOR

(b) OR

(c) NAND

(d) AND

A logic gate is an electronic circuit which

(a) Makes logic decisions

(b) Allows electrons flow only in one direction

(c) Works binary algebra

(d) Alternates between 0 and 1 values

The logic behind ‘NOR’ gate is that it gives

(a) High output when both the inputs are low

(b) Low output when both the inputs are low

(c) High output when both the inputs are high

(d) None of these

Boolean algebra is essentially based on

(a) Truth

(b) Logic

(c) Symbol

(d) Numbers

A truth table is given below. Which of the following has this type of truth table

(a) XOR gate

(b) NOR gate

(c) AND gate

(d) OR gate

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

(a) a

(b) b / a

(c) ba

(d) b

NPN transistor are preferred to PNP transistor because they have

(a) Low cost

(b) Low dissipation energy

(c) Capability of handing large power

(d) Electrons having high mobility than holes

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

(a) 1.1 mA

(b) 1.01 mA

(c) 0.01 mA

(d) 10 mA

While a collector to emitter voltage is constant in a transistor, the collector current changes by 8.2 mA when the emitter current changes by 8.3 mA. The value of forward current ratio h_fe is

(a) 82

(b) 83

(c) 8.2

(d) 8.3

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

(a) Oscillator

(b) FET

(c) Rectifier

(d) Amplifier

In an NPN transistor circuit, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, the emitter current (i_E) and base current (i_B) are given by

(a) iE = – 1 mA, iB = 9 mA	(b) iE = 9 mA, iB = – 1 mA
(c) iE = 1 mA, iB = 11 mA	(d) iE = 11 mA, iB = 1 mA

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

(a) Emitter current will be 9 mA	(b) Emitter current will be 11.1 mA
(c) Base current will be 0.1 mA	(d) Base current will be 0.01 mA

If  are the lengths of the emitter, base and collector of a transistor then

(a)

(b)

(c)

(d)

When NPN transistor is used as an amplifier

(a) Electrons move from base to emitter

(b) Electrons move from emitter to base

(c) Electrons moves from base to emitter

(d) Holes moves from base to emitter

Correct relation for triode is

(a)

(b) μ =

(c) μ =

(d) None of these

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

(a) Collector side is reverse biased and emitter side is forward biased

(b) After electrons are lost in the base and only remaining ones reach the collector

(c) Collector side is forward biased and emitter side is reverse biased

(d) Collector being reverse biased attracts less electrons

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

(a) 0.04 mA

(b) 1.96 mA

(c) 0.98 mA

(d) 2 mA

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

(a) 6 mA

(b) 4.8 mA

(c) 24 mA

(d) 8 mA

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

(a) Base

(b) Emitter

(c) Collector

(d) None of these

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

(a) A common base amplifier circuit	(b) A common emitter amplifier circuit
(c) A common collector amplifier circuit	(d) Neither of the above

The most commonly used material for making transistor is

(a) Copper

(b) Silicon

(c) Ebonite

(d) Silver

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

(a) Smaller

(b) Larger

(c) Same

(d) Not related