Question Text
Question 3 :
How much energy does a 60W electric bulbtransfer in 1 minute?
Question 5 :
In our household applications, commercial unit of electricity is used. One unit is equal to:
Question 6 :
An electric motor operates with an efficiency of $90$%. A pump operated by the motor has an efficiency of $80$%. The overall efficiency of the system is:
Question 7 :
An electric pump takes $30$ minutes to fill a tank of volume $30\ m^{3}$ with water. If the height over which the water is lifted be $30\ m$, and the efficiency of the pump is $50 \%$, the input electric power required by the pump is: (Given $g = 10\  m/$ <br> $s^2$)
Question 9 :
If $\mathrm{R}=6400\times 10^{3}$ m, g $=9.8\mathrm{m}/\mathrm{s}^{2}$, and if the earth were then reassembled rapidly so that no energy is radiated away, the rise in temperature will be (Given that the specific heat s-1 cal/gm/k)<br/>
Question 10 :
If the gravitational force had varied as $r^{-5/2}$ instead of $r^{-2}$; the potential energy of a particle at a distance '$r$' from the centre of the earth would be proportional to
