Valve Electronics Test

Result

Valve Electronics Test - 3

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Question 1
1 / -0

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

Solution

As we know that, Intensity ∝ Number of electrons. Hence, number of secondary electrons emitted per number of primary electrons depends on intensity.
Question 2
1 / -0

In a diode, when there is a saturation current, the plate resistance will be

A
data insufficient

B
zero

C
some finite quantity

D
infinite quantity

Solution

In case of saturation on current, ΔI = 0

Plate resistance = ∞
Question 3
1 / -0

The grid voltage of any triode valve is changed from -1 volt to -3 volt and the mutual conductance is 3× 10⁻⁴ mho. The change in plate circuit current will be

A
0.8 mA

B
0.6 mA

C
0.4 mA

D
1 mA

Solution
Question 4
1 / -0

For the plate voltage, the plate current in a triode valve is maximum when the potential of :

A
The gird is positive and plate is negative

B
The grid is zero and plate is positive

C
The grid is negative and plate is positive

D
The grid is positive and plate is positive

Solution

When grid is given potential more electrons will cross the grid to reach the positive plate p. Hence current increases.
Question 5
1 / -0

The amplification factor of a triode is 20. If the grid potential is reduced by 0.2 volt then 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

Solution

Given:-

Amplification factor = 20

Reduction in grid potential = 0.2V

From the formulae, we know that
Question 6
1 / -0

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

A
Filament

B
Cathode

C
Grid

D
Plate

Solution

The amplification produced by a triode is due to the action of control grid. A triode has three electrodes that are mounted inside an evacuated glass or metal container. These three electrodes comprise a cathode filament, a control grid and an anode plate. Among them, the control grid is the most critical and important electrode because of the amplification factor.
Question 7
1 / -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

Solution
Question 8
1 / -0

The voltage gain of a triode depends upon

A
Filament voltage

B
Plate voltage

C
Plate resistance

D
Plate current

Solution

The voltage gain of a triode depends upon plate resistance.
Question 9
1 / -0

In a triode value

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 double

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

Solution

In a triode value if the temperature of filament is doubled, then the thermionic current will nearly be four times.
Question 10
1 / -0

In the circuit of a triode value, 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 value is

A
15

B
20

C
25

D
35

Solution

Given:-

Plate potential = 200V to 220V

Grid potential= −0.5V to −1.3V

From the formulae, we know that