Final answer:
To determine the heat-loss rate through a slab between a 7 °C ground temperature and a 21 °C interior temperature, we need the specific heat transfer coefficient and slab area, which are not provided. An example is given with a known heat loss rate to explain the concept.
Step-by-step explanation:
To calculate the heat-loss rate through the slab when the ground temperature is 7 °C and the interior of the house is 21 °C, we need to know the heat transfer coefficient (U-value) or heat loss rate per degree Celsius difference and the area of the slab. Without this information, it is impossible to give an exact figure.
However, we can discuss a similar concept using a provided example where a house has a heat loss rate of 200 W/°C.
If it's equipped with a 5,000 W heater and the outside temperature is -10°C, the heater would have to compensate for a temperature difference of 31°C (internal minus external temperature) which leads to a heat loss of 6200 W (200 W/°C × 31°C).
However, since the heater can only provide 5000 W, the inside temperature would eventually fall as the heater cannot fully compensate for the heat loss.