Today we are going to describe – State the construction and graduation of a mercury thermometer. A thermometer is a device that is used to measure temperature. Among different types of thermometers, mercury thermometers are one of the most widely used. A mercury thermometer works based on the principle that mercury expands when heated, and its volume decreases when cooled. This change in volume of mercury is used to measure the temperature of the surroundings.
Construction and graduation of a mercury thermometer
The construction of a mercury thermometer consists of three main parts – a glass bulb, a thin glass tube, and a small quantity of mercury. The bulb is made of glass and is filled with a small amount of mercury. The glass tube is then attached to the bulb by heating the glass and melting it together. The tube is long and thin, and it has a very narrow bore, which allows the mercury to move up and down the tube.
The thermometer is calibrated or graduated by marking a scale on the glass tube. The calibration process involves marking two reference points on the thermometer, one for the freezing point and the other for the boiling point of water. The interval between the two reference points is then divided into equal parts, and each division is marked on the thermometer to indicate the temperature.
To calibrate the thermometer, the bulb is placed in melting ice, which is at a known temperature of 0°C, and the position of the mercury in the glass tube is marked as the freezing point. The thermometer is then placed in boiling water, which is at a known temperature of 100°C, and the position of the mercury is again marked as the boiling point. The distance between these two points is divided into equal parts, and each division is marked on the thermometer.
The graduations on the thermometer are typically marked in degrees Celsius or Fahrenheit, depending on the country’s preference. In the Celsius scale, the freezing point of water is marked at 0°C, and the boiling point is marked at 100°C. In the Fahrenheit scale, the freezing point is marked at 32°F, and the boiling point is marked at 212°F.
The construction and graduation of a mercury thermometer involve three main parts – a glass bulb, a thin glass tube, and a small quantity of mercury. The thermometer is calibrated by marking two reference points on the thermometer, one for the freezing point and the other for the boiling point of water. The interval between the two reference points is then divided into equal parts, and each division is marked on the thermometer to indicate the temperature.
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