Question

Heat is being supplied at a constant rate to a sphere of ice which is melting

Answer 1

your question is incomplete. A complete question is ----> Heat is being supplied at a constant rate to a sphere of ice which is melting at the rate of 0.1 gm/sec. It melts completely in 100 sec. The rate of rise of temperature thereafter will be (Assume no loss of heat.) 1. 0.8 °C/sec 2. 5.4 °C/sec 3. 3.6 °C/sec 4. will not change temperature.

answer : rate of melting of ice , dm/dt = 0.1gm/s

time taken to melt completely , t = 100 sec

actually, during melting process of ice, temperature doesn't change , it remains constant e.g., 0°C . after melting completely, it converts into water.

now, water is present at 0° C . when further we supply heat to water then it will change its temperature.

here, question asked what is the rise of temperature thereafter. of course here will not change in temperature.

so, option (4) is correct.