# Convection

## 06 Feb Convection

Physics tuition classes in Miracle Learning Centre is easy to understand and help you to improve in your grades. If you do not understand physics, you must definitely attend the physics tuition class at Miracle Learning Centre. Let us learn about convection in this physics tuition lesson.

Convection is the transfer of heat energy in a liquid or a gas. Heat, in general, causes substances to expand. On expansion, they become less dense. The fluid near a heat source is heated, becomes less dense, and rises upwards.

The student at Miracle Learning Centre asked, “How does land and sea breeze work?”

The physics tuition teacher at Miracle Learning Centre replied,” Land and sea breezes are actually convection currents. During the day, the land warms up more than the water in the sea. The air over the land becomes less dense and rises upwards. To replace it, the cooler air from the sea moves towards the land. This convection current from the sea to the land is called the sea breeze. The reverse happens during night.”

Ventilation take place in rooms via convection currents. Warm air being less dense rises up and leaves the room through the ventilators provided near the ceiling. To make up this, fresh air from outside enters the room through the doors and windows. The convection current so set in the air helps in keeping the air in the room fresh.

Natural convection heat transfer is extensively used in the following areas. Cooling of commercial high voltage electrical power transformers. Heating of houses by electrical baseboard heaters. Heat loss from steam pipe lines in power plants and heat gain in refrigerant pipe lines in air conditioning applications. Cooling of reactor cores in nuclear power plants, though often the coolant is driven by pumps, resulting in more efficient heat transfer by forced convection. Cooling of electronic devices (chips, transistors) by finned heat sinks, though a fan is often present to augment the natural convection with forced convection.

Household hot-water system works using convection current. Water is heated in boiler by gas burners. Hot water expands and becomes less dense. It rises and flows into upper half of the cylinder. Cold water from the cistern being denser, sinks into the lower half of cylinder and then to boiler. Overflow pipe attached to cylinder just in case temperature of water becomes too high and causes a large expansion of hot water. Hot-Water tap led from overflow pipe must be lower than cistern so that pressure difference between cistern and tap cause water to flow out of tap.

Miracle Learning Centre would like to bring you more articles on Physics tuition concepts. We hope you have understood what convection is. Do come to Miracle Learning Centre for more physics tuition lessons to learn more about convection and physics.