The galvanometer has no deflection and the length of wire $AB$ is $350 \, cm$. Then $AC$ equals to ............... $cm$.

Four ammeters with identical internal resistances $r$ and a resistor of resistance $R$ are connected to a current source as shown in the figure. It is known that the reading of the ammeter $A_1$ is $I_1 = 3\ A$ and the reading of the ammeter $A_2$ is $I_2 = 5\ A$. Determine the ratio of the resistances $R/r$.

In the given current distribution,what is the value of $I$ in $A$?

Three resistances $P, Q, R$ each of $2 \,\Omega$ and an unknown resistance $S$ form the four arms of a Wheatstone bridge circuit. When a resistance of $6 \,\Omega$ is connected in parallel to $S$,the bridge gets balanced. What is the value of $S$ in $\Omega$?

In the arrangement of resistors shown in the diagram,the potential difference between $B$ and $D$ will be zero when the unknown resistance $X$ is ............... $\Omega$.

In the circuit shown below,the ammeter reading is zero. Then the value of the resistance $R$ is (in $Omega$)