Two resistors of $100 \Omega$ each are connected in series with a $9 \text{ V}$ battery. $A$ voltmeter of $400 \Omega$ resistance is connected to measure the voltage drop across one of the resistors. The voltmeter reading is . . . . . . $V$.

Resistors of $1\, \Omega$, $2\, \Omega$, and $3\, \Omega$ are connected in the form of a triangle. If a $1.5\, V$ cell of negligible internal resistance is connected across the $3\, \Omega$ resistor, the current flowing through this resistance will be ................ $A$.

Find the electric potential at points $C$ and $D$ in the given circuit.

The power of an electric motor is $242 \ W$ when connected to a $220 \ V$ supply. When the motor is operated at $200 \ V$,the current drawn by it is (in $A$)

Twelve wires each having resistance $2 \Omega$ are joined to form a cube. $A$ battery of $6 \text{ V}$ emf is connected across points $a$ and $c$. The voltage difference between $e$ and $f$ is . . . . . . $\text{V}$.

Suppose there is a circuit consisting of only resistances and batteries. Suppose one is to double (or increase it to $n$-times) all voltages and all resistances. Show that currents are unaltered.