The same mass of copper is drawn into two wires $1\, mm$ and $2\, mm$ thick. Two wires are connected in series and current is passed through them. Heat produced in the wire is in the ratio
$2:1$
$1:16$
$4:1$
$16:1$
Assertion : Long distance power transmission is done at high voltage.
Reason : At high voltage supply power losses are less.
The emf of a battery is $2\, V$ and its internal resistance is $0.5 \,\Omega$. The maximum power which it can deliver to any external circuit will be ............. $watt$
An electric kettle has two heating coils. When one of the coils is connected to an a.c. sotuce, the water in the kettle boils in $10$ minutes. When the other coil is used the w’ater boils in $40$ minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be ...... $min$
Ametallic conductor of irregular cross-section is as shown in the figure. Aconstant potential difference is applied across the ends $(1)$ and $(2)$. Then :
In the figure shown the power generated in $y$ is maximum when $y = 5\,\Omega$ . Then $R$ is .............. $\Omega$