Three identical resistances $A$,$B$,and $C$ are connected as shown in the given figure. The heat produced will be maximum in:

The effective resistance of two resistors in parallel is $\frac{12}{7} \ \Omega$. If one of the resistors is disconnected,the resistance becomes $4 \ \Omega$. The resistance of the other resistor is ............. $\Omega$.

Two bulbs $X$ and $Y$ having the same voltage rating and power ratings of $40\, W$ and $60\, W$ respectively are connected in series across a potential difference of $300\, V$. Then:

Resistors of $10\, \Omega, 5\, \Omega, 7\, \Omega$, and $3\, \Omega$ are connected along the sides $AB, BC, CD$, and $DA$ of a square, respectively. A resistor of $10\, \Omega$ is connected across the diagonal $AC$. What is the equivalent resistance between points $A$ and $B$ in $\Omega$?

An electric kettle has two filaments. The first filament boils a certain amount of water in $10 \text{ minutes}$ and the second filament boils it in $15 \text{ minutes}$. If both filaments are connected in parallel,the water will boil in .............. minutes.

In the given circuit,the current flowing through the resistance $20 \ \Omega$ is $0.3 \ A$,while the ammeter reads $0.9 \ A$. The value of $R_1$ is . . . . . . $\Omega$.