And the height the mercury rises to is a convenient measure of atmospheric pressure and can be read off using a simple ruler. We could use mm of water, but would need a much longer tube and an unusually inconveniently sized ruler. Hence why mercury is the fluid and a convenient way of measuring pressure is mm of Hg.
Why is pressure measured in mercury?
Mercury is commonly used in barometers because its high density means the height of the column can be a reasonable size to measure atmospheric pressure . ... A barometer using water, for instance, would need to be 13.6 times taller than a mercury barometer to obtain the same pressure difference.
Why is mercury in mmHg?
Moreover, we denote it with mmHg or mm Hg. In this the mm represents millimetre and Hg is the chemical name of mercury or the symbol for mercury. ... In addition, one millimetre of mercury is approximately 1 Torr which is 1 / 760 of standard atmospheric pressure (101325 / 760 ≈ 133.322368421053 Pascals).
Why do we use mm of mercury?
MmHg means millimetres of mercury (Hg = mercury) and is used in EU member states and Switzerland to measure the pressure of body fluids, such as eg blood pressure . ... The unit mmHg (millimeter mercury column) is also used to measure blood pressure.
Why do doctors use mmHg?
As mercury is so much denser than water or blood , even very elevated blood pressures result in it rising no more than about a foot. This quirk of medical history gives us the modern measurement unit for blood pressure: millimetres of mercury (mmHg).
What is normal mmHg?
A healthy blood pressure reading should be lower than 120/80 mmHg . Normal blood pressure is less than 120 mmHg systolic and 80 mmHg diastolic (see blood pressure chart below), and may vary from 90/60 mmHg to 120/80 mmHg in a healthy young woman. A blood pressure of 140/90 mmHg or higher indicates high blood pressure.
What does 120 mmHg reading indicate?
A blood pressure reading above 180/120 mm Hg indicates a serious health problem. The AHA refers to these high measurements as a “ hypertensive crisis .” Blood pressure in this range requires urgent treatment even if there are no accompanying symptoms.
Can a 100 pound woman exert?
Is it possible for a 100-lb woman to exert a greater pressure on the ground than a 250-lb man? ... Yes, the woman can exert a greater pressure than the man if she puts her weight on a small area such as on narrow spike heels.
How is mmHg calculated?
As discussed earlier we know that one millimetre of mercury is the pressure exerted by a 1mm vertical column of mercury at 0 degree Celsius. And we also know that one mmHg is also equal to 1 torr , which is 1 / 760 of atmospheric pressure (atm) that is 1 atm = 760 mmHg.
Why water is not used in barometer?
Water is not a suitable barometric liquid because: (i) The vapour pressure of water is high, so its vapours in the vacuum space will make the reading inaccurate . (ii) Water sticks with the glass tube and wets it, so the reading becomes inaccurate.
What is measured in millimeters of mercury?
Blood pressure is measured in millimeters of mercury (mm Hg).
What mmHg means?
Blood pressure is measured in units of millimeters of mercury (mmHg). The readings are always given in pairs, with the upper (systolic) value first, followed by the lower (diastolic) value.
Is mmHg a Torr?
Pressure Units and Conversion
A barometer measures gas pressure by the height of the column of mercury. One unit of gas pressure is the millimeter of mercury (mmHg). An equivalent unit to the mmHg is called the torr , in honor of the inventor of the barometer, Evangelista Torricelli.
What is the right blood pressure by age?
| Age SBP DBP | 21-25 120.5 78.5 | 26-30 119.5 76.5 | 31-35 114.5 75.5 | 36-40 120.5 75.5 |
|---|
What is the normal reading of human blood pressure?
What are normal blood pressure numbers? A normal blood pressure level is less than 120/80 mmHg . No matter your age, you can take steps each day to keep your blood pressure in a healthy range.
When a patient’s blood pressure is much higher than it should be a doctor?
Answer From Sheldon G. Sheps, M.D. You could have a condition known as white coat hypertension . White coat hypertension occurs when the blood pressure readings at your doctor’s office are higher than they are in other settings, such as your home.
