MELab1 quiz 2 reviewer

Pressure

Pressure

is the force exerted on a region, measured in Newtons per squaremeter(N/m²). It is often used to measure weight applied to a one-inch square, such as 25 pounds per square inch. The SI unit for pressure is Pascal, equivalent to 1 N/m2.

positive pressure

When the force is applied to an object, this is called

negative pressure

When the object is pulled rather than pushed what pressure occurs

Absolute pressure

is the pressure measured wrt a
vacuum (unit = psia)

Gauge pressure

the pressure measured wrt atmospheric pressure (unit = psig)

Atmospheric pressure

the pressure on the earth's surface due to the weight of gases in the earth's atmosphere (14.7psi)

Hydrostatic pressure

-the pressure in a liquid.

-The pressure increases as the depth in a liquid increases, due to its weight.

-Interm of equation, P = pgh

Manometer

measures static pressure by comparing the height of fluid in two columns. When connected to a pressure line, the inlet pressure can be expressed in inches of fluid.

Elastic Elements

such as diaphragms, capsules, bellows, bourdon, or helical tubes, deform under pressure, which can be measured using mechanical or electrical means.

Electrical Resistance pressure gauge

The concept of operation is based on electrical resistance change in a conductor when applied directly to a pressure. The sensing element consist of a loosely wound coil of relatively fine wire, and it will be compressed when high pressure applied on it.

McLeod Gauge

It compresses the low pressure gas so that the increased pressure can be measured. The change in volume and pressure can then be used to calculate the original gas pressure, providing that the gas not condensed.

Pirani Gauge

It consist of platinum filament and thermocouple enclosed in a chamber. The pressure measurement is based on the relation of heat conduction and radiation from a heating element to the number of gas molecules per unit volume in the low pressure region.

Ionization Gauge

can be used to measure pressure down to about 2torr. The gas is ionized with a beam of electrons and the current is measured between two electrodes in the gas.

Temperature

The measurement of heat exchange When the movement of molecules in a substance increases, we experience heat or a rise in temperature. When there is friction in a system, when there is combustion, or when there is an increase in pressure on a vessel, the temperature rises.

273 degrees Celsius (460 degrees Fahrenheit)

Absolute zero is what temp?

thermometer

Instruments those are measuring ordinary temperature is known as

pyrometer

Instruments those are measuring higher temperature is known as

absolute zero temperature

It is found that at particular temperature the gas will not occupy any volume, this temperature is known as

absolute temperature.

The temperature measured with reference to absolute zero temp Is known as

273.15 °C

The point of absolute zero temperature is found to occur at

• Liquid in Glass Thermometer

• Bimetallic Element.

Change in Physical Dimensions

• Constant Volume Gas thermometer

• Pressure thermometer

Change in Gas or Vapour Pressure

• Resistance Thermometer (RTD,PRT)

• Thermistors

• Thermocouples

• Semiconductor -Junction sensors

  • Diodes

  • Integrated circuits

Change in Electrical Properties:

• Thermal and Photon sensors

• Total Radiation Pyrometers.

• Optical pyrometer

• Infrared pyrometer

Change in Emitted thermal Radiation:

• Fusible indicators

• Liquid crystals

• Temperature reference cell

Change in Chemical Phase

Change in Physical Dimension Thermometer

• This type of thermometer is also known as Expansion Thermometer

• This type of thermometer has the scale engraved directly on the glass stem.

Pressure Thermometer

the thermometer consists of a bulb which contains bulk of the fluid .
The bulb is placed in the region whose temperature is required. A capillary tube connects the bulb to a bourdon tube, which is graduated with a temperature scale.

• Vapour pressure thermometer

• Liquid-filled thermometer

• Gas-filled thermometer

Types of pressure thermometer

Electrical resistance Thermometer

measure temperature by measuring the resistance of known metals. They are used over a temperature range of 200°C to 650°C. As temperature increases, electrical resistance of most metals increases in proportion. Measurement of resistance in a wire can determine its temperature. The resistance element should be high temperature coefficient, reproducible, stable, and resistant to corrosion and oxidation.