AP EAMCET Engineering 21 Apr 2019 Shift 1 Paper

The walls of a closed cubical box of edge 60 cm are made of material of thickness 1 mm and thermal conductivity 4 x 10−4cals−1cm−1°C−1. The interior of the box is maintained 1000 °C above the outside temperature by a heater placed inside the box and connected across 400 V DC supply. The resistance of the heater is