What will be the equivalent resistance between points $A$ and $B$ of the following electric circuit?

Define electric power. Give its $SI$ units and write its mathematical equation.

Draw a schematic diagram of a circuit consisting of a cell of $1.5 \, V$, a $10 \, \Omega$ resistor, a $15 \, \Omega$ resistor, and a plug key, all connected in series.

$A$ wire of length $L$ and resistance $R$ is stretched so that the length is doubled and area of cross-section is halved. How will its
$(a)$ resistance change?
$(b)$ resistivity change?

$(a)$ For the circuit shown in the diagram,calculate:
$(i)$ The value of current through the $30\, \Omega$ resistor.
$(ii)$ The total resistance of the circuit.
$(b)$ Give two advantages of connecting electrical devices in parallel with a battery.

$(a)$ Explain how a cell maintains current in a circuit.
$(b)$ In the circuit given below,the resistance of the path $xTy = 2 \, \Omega$ and that of $xZy = 6 \, \Omega$.
$(i)$ Find the equivalent resistance between $x$ and $y$.
$(ii)$ Find the current in the main circuit.
$(iii)$ Calculate the current that flows through the path $xTy$ and $xZy$.