Two resistances $20\,\Omega$ and $50\,\Omega$ and a pure inductance of $50\,H$ are connected to a $10\,V$ battery through a key as shown in the figure. The key is closed at $t = 0$. Find the final value of current in the $50\,\Omega$ resistor.

When a certain circuit consisting of an emf $E$,an inductance $L$,and a resistance $R$ is closed,the current in it increases with time according to curve $1$. After one parameter ($L$ or $R$) is changed,the increase in the current follows curve $2$,when the circuit is closed a second time. Which parameter was changed?

Calculate the current,a long time after the closing of the key $K$ in a circuit containing a battery of $10 \ V$,a resistor of $2 \ \Omega$,and an inductor of $5 \ H$. (in $A$)

The time taken for the magnetic energy to reach $25\%$ of its maximum value,when a solenoid of resistance $R$ and inductance $L$ is connected to a battery,is:

In an $L-R$ circuit,the current reaches $\frac{3}{4}$ of its maximum value in $4 \ s$. What is the time constant of the $L-R$ circuit?

The figure shows three circuits with identical batteries,inductors,and resistors. Rank the circuits according to the currents through the battery just after the switch is closed,greatest first.