Convection

Q. A resistance of $20\Omega$ is connected to a 40 V battery. Calculate the heat energy in joules generated per minute.

Q.

Assuming Newton's law of cooling to be valid, the time taken by a body to cool from a temperature $T_1$ to a temperature $T_2$ in a room where the temperature is $T_0$ $(T_0<T_2<T_1)$ is proportional to

1. $lo{g}_e\left(\frac{T_1-T_0}{T_2-T_0}\right)$

2. $lo{g}_e\left(\frac{T_2-T_0}{T_1+T_0}\right)$

3. $lo{g}_e\left(\frac{T_1-T_2}{T_0}\right)$

4. $lo{g}_e\left(\frac{T_1+T_0}{T_2+T_0}\right)$

Q. A solid shpere and a hollow sphere of the same material and of equal radii are heated to the same temperature

1. both will emit equal amount of radiation per unit time in the beginning.
2. both will absorbs equal amount of radiation per second from the surrounding in the beginning.
3. the initial rate of cooling will be the same for both the spheres
4. the two spheres will have equal temperature at any instant