Two wires of the same material and length but different cross-sectional areas are connected in series across a battery. If the ratio of their radii is 2:1, what is the ratio of the power dissipated in them?

In $Cu - Fe$ couple, the flow of current at the temperature of inversion is

Two heater wires of equal length are first connected in series and then in parallel. The ratio of heat produced in the two cases is

When a current is passed in a conductor, 3\,{\,^0}{\rm{C}} rise in temperature is observed. If the strength of current is increased by two times, then rise in temperature will approximately be

Forty electric bulbs are connected in series across a $220\,\,V$ supply. After one bulb is fused, the remaining ${\rm{39}}$ are connected again in series across the same supply. The illumination will be

A house, served by ${\rm{220}}\,\,{\rm{V}}$ supply line, is protected by a ${\rm{9}}\,\,{\rm{A}}$ fuse. The maximum number of ${\rm{60}}\,\,{\rm{W}}$ bulbs in parallel that can be turned on is

In a house there are 4 bulbs each of $50W$ and 5 fans each of $60W$. If they are used at the rate of 6 hours a day, the electrical energy consumed in a month of 30 days is

A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be

An electric bulb is rated $60\,\,W,\,\,220\,\,V$. The resistance of its filament is

If two electric bulbs have $40\,\,W$ and $60\,\,W$ rating at $220\,\,V$, then the ratio of their resistances will be

When a current passes through the junction of two different metals, evolution or absorption of heat at the junction is known as