Changes between Version 3 and Version 4 of ElectricalIntroduction

Timestamp:

Aug 20, 2017, 10:21:54 PM (8 years ago)

Author:

David Albert

Comment:

--

ElectricalIntroduction

@@ -10 +10 @@
 * The battery terminal that consumes electrons is called the positive terminal and is usually marked with a red color or '+' sign.
 
-=== Voltage ===
-The difference in electrical potential between the two terminals is measured in units of Volts (named after [https://en.wikipedia.org/wiki/Alessandro_Volta Alessandro Volta]).  Voltage is *potential* energy, like the lake behind a hydroelectric dam; no work is being done if the water isn't flowing, but you can measure the pressure the water is exerting on the dam.  You can use a meter called a voltmeter or a multimeter to measure the amount of voltage "pressure" a battery exerts.  [[Image(http://wiki.team2537.com/attachment/wiki/ElectricalIntroduction/UT136B.jpg, align=right)]]
+=== Voltage === 
+The difference in electrical potential between the two terminals is measured in units of Volts (named after [https://en.wikipedia.org/wiki/Alessandro_Volta Alessandro Volta]).  Voltage is *potential* energy, like the reservoir/lake behind a hydroelectric dam; no work is being done if the water isn't flowing, but you can measure the pressure the water is exerting on the dam.  It's important to recognize that voltage is just a potential, no work is being done by voltage, it represents a difference in charge, the strength of attraction between two opposite charges.  There are many different types of batteries that use different types of chemical reactions to generate that charge potential difference.  The oldest type of battery, and the one we still use on our robots, is the [https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery lead-acid] battery which uses lead terminals and sulphuric acid.  These batteries produce 2 volts per cell; if you put 6 of them together in sequence, you can get 12 volts. 
 
-* Exercise: Use a multimeter to measure the voltage of a battery:
-    * Turn the multimeter on and move the range selector to DC Volts (often shown as a dashed line over a solid line)
+You can use a meter called a voltmeter or a multimeter to measure the amount of voltage "pressure" a battery exerts. 
+
+[[Image(UT136B.jpg,left,20%,nolink)]] [[Image(Cen-Tech_Multimeter.jpg,20%,nolink)]]
+
+* Exercise: Use a multimeter to measure the voltage of a battery:  
+    * Turn the multimeter on and move the range selector knob to DC Volts (often shown as DCV or a dashed line over a solid line)
     * Plug the black wire into the hole labeled COM
     * Plug the red wire into the hole labeled V/mA/...
@@ -21 +25 @@
     * The multimeter will display the battery voltage 
 
+* What happened: the electrical pressure, (the difference in positive vs. negative charge) between the two terminals is measured by the multimeter and displayed.  Virtually no energy is consumed from the battery in making this measurement.
+
 === Current ===
+[[Image(https://swcphysics30.files.wordpress.com/2013/01/tim1.jpg?w=768&h=514,right,20%,nolink)]]
 When electrons are allowed to flow between the positive and negative battery terminals, we have a *circuit* and the battery's chemical reaction proceeds (until the chemical reaction is complete).  The number of electrons flowing between the terminals is called "Current" and is measured in [https://en.wikipedia.org/wiki/Ampere Amperes] aka Amps (named after [https://en.wikipedia.org/wiki/Andr%C3%A9-Marie_Amp%C3%A8re André-Marie Ampère].  The number of electrons flowing depends on how many electrons the battery can supply (how fast the chemical reaction can proceed) and the nature of the path carrying the electrons from one terminal to the other.  You can measure current using your multimeter in the next section.