a heat and the temperature change

The figure shows a household radiant heater[即係好似有個網個d暖爐]. The heater is placed on the floor of an empty room of dimension 3 m * 3 m * 3 m. The heater is switched on.

(a)If the air density under standard conditions is 1.29 kg m^-3, what is the mass of air in this room? (Assume the volume of the heater is negligible.)(2 M)

(b) The heater operates at a power of 1500 W. The specific heat capacity of air is about 1000 J kg^-1 oC^-1. If the heater is switched on for an hour, estimate the rise in temperature of the air in the room. (Assume the volume of air does not change and the heater is 100% efficient.)(3 M)

(c)Practically, the temperature rise is far less than that in (b). One of the reasons is that some of the energy is lost to the surroundings. Suggest another reason.(1 M)


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