According to Joule's law of heating, the heat produced in any resistor is inversely proportional to the resistance of the resistor.

Find the ratio of resistances for two bulbs of $220 \mathrm{V}-60 \mathrm{W} \mathrm{and} 110 \mathrm{V}-60 \mathrm{W}$.

Write joule's law related to the heating effect of the current.

Consider the following assertion ($a$) and the reason ($r$). Select the correct alternative :

Assertion ($a$): When high voltage power is supplied through a domestic wiring, immediately the running television (ON condition) will burn out.

Reason ($r$): DP switch is fitted in domestic wiring to cut - off the power supply automatically when high voltage is supplied.

Correct the statements by modifying the underlined words appropriately if it is wrong.

In the incandescent lamps, vaporisation of filaments can be reduced by using hydrogen or nitrogen at low pressure.

Give three characteristics of the material for the heating element.

In the circuit shown, the heat produced in $5 \mathrm{\Omega }$ resistor is $10 \mathrm{cal} {\mathrm{s}}^{-1}$. The heat produced per sec in $4 \mathrm{\Omega }$ resistor will be