Topic 2 Part 2 Devices for measuring temperature

Topic 2 Part 2 – Devices for measuring temperature

The Kelvin Scale �After the creation of the Celsius scale, the Kelvin scale was created because new gases were being discovered. ◦ Scientists required a more accurate reading of high and low temperatures.

Absolute Zero �Absolute zero is the coldest possible temperature ◦ Absolute zero on the Celsius scale is 273. 15 o. C ◦ Absolute zero on the Kelvin scale is 0 K

What is the difference between heat and temperature �Heat is a measure of energy of the particles moving around ◦ Thermal Energy is HEAT! �Temperature is a measure of how hot or cold something is measured on a scale like a thermometer.

Different thermometers have been developed over time �They suit different purposes:

How does a thermometer work? �Explain in general how a thermometer works using the terms sensor, signal and responder. ◦ Page 199 �Sensor: a material which responds to temperature change (ie: alcohol) �Signal: Information about the temperature (ie: scale) �Responder: A pointer, light or other mechanism that uses the signal (ie: level alcohol reaches)

Video: Eurika Science! �Eurika! heat vs. temperature

Thermocouple �Description ◦ - wires of two different metals are twisted together (copper and iron) ◦ - when heated it produces an electrical current �Use ◦ - turn switch on or off it temperature changes �Reason for Development ◦ - measures high temperatures ◦ - cannot be used to measure low temperatures

Bimetallic Strip �Description ◦ - two metals fused together ◦ - expands at different rates ◦ - coils when heated - reverses when cools �Use ◦ - operates electrical switches ◦ - controls furnace (thermostat), air conditioner, fridge �Reason for Development ◦ - easy way to turn something on and off automatically

Recording Thermometer �Description ◦ - a bimetallic strip joined to a lever with a pen �Use ◦ - records small movement of temperature change ◦ - weather records �Reason for Development ◦ - records temperature over a period of a

Infrared Thermogram �Description ◦ electronic sensor or device that photographs temperature change through colour ◦ photographs radiation �Use ◦ detects air leaks ◦ energy efficient ◦ can be used to predict dangers of over heating �Reason for Development ◦ detects precise temperature change - not visible to the eye ◦ quick and accurate

To measure temperature � 1. Thermometer � 2. Thermocouple � 3. Bimetallic Strip � 4. Recording Thermometer � 5. Infrared Thermogram

Eurika Science! �Eurika: Measuring Temperature

Thinking time! �Which tool for measuring and controlling temperature would be most affective? � 1. Controlling an electric frying pan? � 2. Making long term records at the weather office? � 3. Detecting small forest fires before they spread?

Controlling a fry pan bimetallic strip

Long term records Recording Thermometer

Forest Fire Infrared Thermogram