Question

The radiation of an electric room heater is most effective when it is:
A. uncleaned
B. polished to shine
C. painted green
D. painted black

Answer 1

As a first step, you could explain what exactly an electric heater is and also mention its working principle. Then you could think of the factors that will help in increasing the efficiency of an electric heater. Thus, you could determine which among the given factors adds to the effectiveness of it.

Complete solution:
In the question, we are asked to find which of the given factors make the radiation of an electric room heater most effective. Before answering that let us understand what exactly a room heater is.

Electric heater is a device that is based on the principle of Joule heating. This electric device converts the electrical energy into heat energy. The heating element is found to be an electrical resistor. There are many ways in which room heating can be done. We could use infrared radiant heaters, convection heaters, fan heaters, storage heating, domestic electrical underfloor heating and heat pumps.

We know that the electric heaters are known to be 100% efficient as it can convert most of its energy to heat. Also in comparison with rough dark surfaced electric room heaters with the highly polished ones scientists have come to the conclusion that the highly polished ones take more time to cool down thereby retaining the heat for a long time. This feature makes them more effective. Hence, option B is found to be the correct answer.

Note:
The room heaters have great significance in the places where air handling is found to be difficult. These devices can be set at different temperatures as per convenience at low, medium and high. Normally, these resistors that act as heating elements would be a metal alloy wire like the nichrome wire.