A 50 mm × 45 mm × 20 mm cell phone charger has a surface temperature of Ts = 33°C when plugged into an electrical wall outlet but not in use. The surface of the charger is of emissivity ε = 0.92 and is subject to a free convection heat transfer coeffcient of h = 4.5 W/m2 ⋅K. The room air and wall temperatures are T[infinity] = 22°C and Tsur = 20°C, respectively. If electricity costs C = $0.18/kW ⋅ h, determine the daily cost of leaving the charger plugged in when not in use.

Consider a large isothermal enclosure that is maintained at a uniform temperature of 2000 k. calculate the emissive power of the radiation that emerges from a small aperture on the enclosure surface. what is the wavelength ? , below which 10% of the emission is concentrated? what is the wavelength ? 2 above which 10% of the emission is concentrated? determine the wavelength at which maximum spectral emissive power occurs. what is the irradiation incident on a small object placed inside the enclosure?