A block of heat capacity 120 J/°C is in a room at 20°C. When a heater is switched on, the block warms at 1.5°C/s initially. At 45°C the heater is switched off and the block cools at 0.3°C/s. Assume Ne

Question

A block of heat capacity 120 J/°C is in a room at 20°C. When a heater is switched on, the block warms at 1.5°C/s initially. At 45°C the heater is switched off and the block cools at 0.3°C/s. Assume Newton\'s law of cooling. Find the thermal power the block loses at 32.5°C, in W.

TestHub · Accepted Answer

At 45°C the loss is 120 × 0.3 = 36 W with excess 25°C. At 32.5°C the excess is 12.5°C, so the loss is 36 × 25 12.5 ​ = 18 W. (The heater power is 120 × 1.5 = 180 W.)

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