Why is a vacuum needed in a vacuum tube?
(N/A) vacuum is required in a vacuum tube to prevent the collision of electrons with air molecules. If air were present,the electrons emitted from the cathode would collide with gas molecules,causing ionization and scattering. This would lead to a decrease in the electron current and could cause electrical discharge or arcing,which would damage the tube and prevent it from functioning as a controlled electronic device.
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Similar Questions
For a triode,$\mu = 64$ and $g_m = 1600 \, \mu \text{mho}$. It is used as an amplifier and an input signal of $1 \, V \text{ (rms)}$ is applied. The signal power in the load of $40 \, k\Omega$ will be......$mW$.
Difficult
View SolutionThe plate resistance of a triode is $2.5 \times 10^{4} \ \Omega$ and mutual conductance is $2 \times 10^{-3} \ \text{mho}$. What will be the value of the amplification factor?
Easy
View SolutionWhen the plate voltage in a diode valve is increased from $100 \, V$ to $150 \, V$, the plate current increases from $7.5 \, mA$ to $12 \, mA$. The dynamic plate resistance will be.... $k \, \Omega$.
Medium
View SolutionThe plate resistance of two triode valves is $2 \, k\Omega$ and $4 \, k\Omega$. The amplification factor of each valve is $40$. The ratio of voltage amplification,when used with a $4 \, k\Omega$ load resistance,will be:
Medium
View SolutionThe linear portions of the characteristic curves of a triode valve give the following readings. The plate resistance is ....... $\Omega$.
$V_g$ (volt) $0$ $-2$ $-4$ $-6$ $I_p$ (mA) for $V_p = 150$ $V$ $15$ $12.5$ $10$ $7.5$ $I_p$ (mA) for $V_p = 120$ $V$ $10$ $7.5$ $5$ $2.5$
| $V_g$ (volt) | $0$ | $-2$ | $-4$ | $-6$ |
| $I_p$ (mA) for $V_p = 150$ $V$ | $15$ | $12.5$ | $10$ | $7.5$ |
| $I_p$ (mA) for $V_p = 120$ $V$ | $10$ | $7.5$ | $5$ | $2.5$ |
Difficult
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