What principle is used in a mercury thermometer?
Detailed Solution. Mercury thermometers are based on the principle that liquids expand when heated and contract when cooled. So, when the temperature increases, the mercury expands and rises up the tube and when the temperature decreases it contracts and does the opposite.
What is the working principle of thermometer?
thermal expansion
These liquid thermometers are based on the principal of thermal expansion. When a substance gets hotter, it expands to a greater volume. Nearly all substances exhibit this behavior of thermal expansion. It is the basis of the design and operation of thermometers.
Why does mercury rise in a thermometer?
The mercury pools in the bulb, but when it heats up, it expands. Because it can’t expand through the bottom of the bulb, it is forced up the tube. That expansion, caused by the atoms flying around faster and taking up more space, is what makes the thermometer work.
Which law is used in thermometer?
The Zeroth Law of Thermodynamics
The Zeroth Law of Thermodynamics defines temperature and makes thermometers possible.
On which principle is a thermometer based for Class 8?
Thermometer is based on the principle of, ‘ when a body is heated it expands and when a body is cooled it contracts ‘.
Does a thermometer have mercury?
The oldest thermometers used are mercury in glass. Newer thermometers include non-mercury liquids in glass and digital and electronic devices that use sensors to measure temperature. Thermometers that check body temperature in the ear, across the forehead, or have a digital display do not contain mercury.
What is the principle of liquid in glass thermometer?
Liquid-in-glass thermometers are based on the principle of thermal expansion of substances. A liquid in a glass tube (called a capillary) expands when heated and contracts when cooled. A calibrated scale can then be used to read off the respective temperature that led to the corresponding thermal expansion.
Do all thermometers have mercury?
But not all thermometers with silver liquid contain mercury. If the thermometer has silver liquid and is not labeled as “mercury-free,” assume it contains mercury. Mercury can be poisonous in certain situations. Most oral and rectal thermometers contain about 0.5-0.6 grams of mercury.
How much mercury is in a thermometer?
The mercury will evaporate and can contaminate the surrounding air and become toxic to humans and wildlife. Each thermometer contains about . 5-1.5 grams of mercury.
What does Zeroth law state?
The zeroth law of thermodynamics states that if two bodies are each in thermal equilibrium with some third body, then they are also in equilibrium with each other.
Why is Zeroth law important?
Significance: This law signifies that temperature is a fundamental indicator of thermal equilibrium. If two bodies of the same temperature come in contact with each other then there is no net exchange of heat and those two bodies are said to be in thermal equilibrium.
Why is mercury used in thermometer Class 7?
We use mercury in thermometers because most metals are good conductor of heat and mercury is the only metal in liquid state. It expands as per temperature and has high coefficient of expansion.
