Two metal cubes A and B of same size are arranged as shown in Figure. The extreme ends of the combination are maintened at the indicated temperatures. The arrangement is thermally insulted. The coefficients of thermal conductivity of A and B are `300W//m ^@C and 200 W//m^@C,` respectively. After steady state is reached the temperature t of the interface will be ......

Answer

C

Explanation

The heat transferred through A per second
`Q_1=K_1A(100-t)`
The heat transferred through B per second
`Q_2=K_2A(t-0)`
At steady state `K_1A(100-t)=K_2A(t-0)`
`rArr 300(100-t)=200(t-0) rArr 300-3t=2t rArrt=60^@C`