When a semiconducting device is connected in series with a battery and a resistance, a current is found to flow in the circuit. If, however, the polarity of the battery is reversed, practically no current flows in the circuit. The device may be

For the circuit shown in the figure,the equivalent resistance between points $A$ and $B$ for two cases $(i)$ $V_A > V_B$ and (ii) $V_B > V_A$ is $\qquad \Omega$ and $\qquad \Omega$ respectively. ($D_1$ and $D_2$ are ideal diodes)

$A$ 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?

$A$ junction diode has a resistance of $25 \Omega$ when forward biased and $2500 \Omega$ when reverse biased. The current in the diode, for the arrangement shown, will be

$A$ $p-n$ junction diode can withstand up to $20 \, mA$ current under forward bias. The diode has a potential difference of $0.5 \, V$ across it, which is assumed to be independent of current. What is the maximum voltage of the battery used to forward bias the diode when a resistance of $125 \, \Omega$ is connected in series with it (in $V$)?

In the following electrical circuit, the reading in the milliammeter is (Take knee voltage of silicon diode $= 0.7 \text{ V}$) (in $\text{ mA}$)