Five identical electric filament lamps numbered $1$ to $5$ are joined in parallel across an ideal source as shown in the figure. When all the bulbs are working, the reading in the ammeter is $3 \,A$. When lamp '$1$' is switched off, the reading of the ammeter is (in $\,A$)

$A$ ring is made of a wire having a total resistance $R_0 = 12\,\Omega$. Find the ratio of the lengths $\frac{\ell_1}{\ell_2}$ of the two arcs between points $A$ and $B$ as shown in the figure,such that the equivalent resistance $R$ of the circuit between these points is $\frac{8}{3}\,\Omega$.

Let there be $n$ resistors $R_1, \dots, R_n$ with $R_{\max} = \max \{R_1, \dots, R_n\}$ and $R_{\min} = \min \{R_1, \dots, R_n\}$. Show that when they are connected in parallel,the resultant resistance $R_p < R_{\min}$ and when they are connected in series,the resultant resistance $R_s > R_{\max}$. Interpret the result physically.

Find the equivalent resistance between $P$ and $Q$. (If each wire has a resistance $R$)

Two resistances are joined in parallel whose resultant is $6/8 \, \Omega$. One of the resistance wires is broken and the effective resistance becomes $2 \, \Omega$. Then the resistance in ohm of the wire that got broken was:

An electric heater and an electric bulb are rated $500\, W, 220\, V$ and $100\, W, 220\, V$ respectively. Both are connected in series to a $220\, V$ $a.c.$ mains. The current in the circuit when both are connected in series is ................ $A$.