Answer:
t = 4.0 min
Explanation:
given data:
diameter of rod = 2 cm
T_1 = 100 degree celcius
Air stream temperature = 20 degree celcius
heat transfer coefficient = 200 W/m2. K
WE KNOW THAT
copper thermal conductivity = k = 401 W/m °C
copper specific heat Cp = 385 J/kg.°C
density of copper = 8933 kg/m3
charateristic length is given as Lc




Biot number is given as 

Bi = 0.0025
As Bi is greater than 0.1 therefore lumped system analysis is applicable
so we have
............1
where b is given as



b = 0.01163 s^{-1}
putting value in equation 1

solving for t we get
t = 4.0 min
Current would increase <span>proportionally to voltage. </span><span> Power dissipation (heating) would increase with the square of the voltage. And resistance means, "</span><span>the refusal to accept or comply with something"</span>
No, because in oxygen depraved rooms, if you drop a feather and a bowling ball at the same height and time, they will fall at the same speed and have the same amount of impact.
Answer: Approximately 65% from what i have learnt.
Longitudinal, because the sound can only travel at one direction