$A$ heater coil is cut into two equal parts and only one part is used in the heater. What is the ratio of the heat produced by the half coil to that produced by the original full coil?

$A$ student connects a voltmeter,ammeter,and resistance according to the circuit given. If the voltmeter reading is $20\, V$ and the ammeter reading is $4\, A$,then the resistance $R$ will be:

In the given circuit,what is the voltage between $P$ and $Q$ in $V$?

Two voltameters,one of copper and another of silver,are joined in parallel. When a total charge $q$ flows through the voltameters,equal amounts of metals are deposited. If the electrochemical equivalents of copper and silver are $z_1$ and $z_2$ respectively,the charge which flows through the silver voltameter is

In the figure,the value of the resistor to be connected between $C$ and $D$ so that the equivalent resistance of the entire circuit between $A$ and $B$ does not change with the number of elementary sets used is

In the adjoining circuit, the battery $E_1$ has an $e.m.f.$ of $12 \, V$ and zero internal resistance, while the battery $E_2$ has an $e.m.f.$ of $2 \, V$. If the galvanometer $G$ reads zero, then the value of the resistance $X$ in $ohms$ is