Heat can be transferred in a room by convection - Leaving Cert Physics - Question 7 - 2006

To demonstrate convection in a liquid, set up a beaker filled with water and place a heat source, such as a burner, beneath it. Introduce a dye or food coloring at one side of the beaker. As the water heats up, observe how the colored water rises and spreads, indicating convection currents.

Insulation is used to reduce heat loss from the bricks to the environment, ensuring that more heat remains within the heater. Materials such as fiberglass, rock wool, or aerogel can be used as insulation.

The storage heater heats the air by conduction. When the heating coil within the bricks is energized, the heat is transferred to the bricks, which then conduct heat to the surrounding air. The warm air then rises and circulates in the room, distributing the heat.

The energy gained by the bricks can be calculated using the formula: $Q = mc heta$,
where:

• m = mass of bricks = 80 kg
• c = specific heat capacity = 1500 J kg⁻¹ K⁻¹
• heta = change in temperature = (300°C - 15°C) = 285 K.

Thus,
$Q = 80 imes 1500 imes 285 = 34,200,000 ext{ J}$.

The power of the heating coil can be calculated using the total energy and time. Power (P) is given by:
P = rac{Q}{t},
where Q = 34,200,000 J and t = 10 hours = 36,000 seconds.
Thus,
P = rac{34,200,000}{36,000} = 950 ext{ W}.