Sunday, 7 October 2012

More About Electricity Basic Terms

 What’s an Electron?

An electron is one of the three fundamental parts of a molecule, the
other two are the proton and the neutron. One or more protons and neutrons stick together in the center of the molecule in an area called the nucleus. Electrons are very small in comparison to protons and neutrons, and they orbit around the nucleus. Electrons repel each other, and electrons and protons attract to each other.


What’s Charge? 

The tendency for an electron to repel from another electron and attract to
a nearby proton is called negative charge. The tendency for a proton to repel from another proton and attract an electron is called positive charge. When a molecule has more electrons than protons, it is said to be negatively charged. If a molecule has less electrons than protons, it is said to be positively charged. If a molecule has the same number of protons and electrons, it is called neutrally charged.

What’s Voltage? 

Voltage is like electrical pressure. When a negatively charged molecule is
near a positively charged molecule, the extra electron on the negatively charged molecule tries to get from the negatively charged molecule to the positively charged molecule. Batteries keep a compound with negatively charged molecules separated from a compound with positively charged molecules. 
Each of these compounds is connected to one of the battery’s terminals, the positively charged compound is connected to the positive (+) terminal, and the negative compound is connected to the negative (-) terminal. The volt is a measurement of electric pressure, and it’s abbreviated with a capital V. You may already be familiar with a nine volt (9 V) battery used to supply power to the Board of Education or HomeWork Board. Other common batteries include the 12 V batteries found in cars and the 1.5 V AA batteries used in calculators, handheld games, and other devices.

What’s Current? 

Current is a measure of the number of electrons per second passing through a circuit. Sometimes the molecules bond in a chemical reaction that creates a compound (that is neutrally charged). Other times, the electron leaves the negatively charged molecule and joins the positively charged molecule by passing though a circuit like the one you just built and tested. The letter most commonly used to refer to current in schematics and books is capital ‘I’.

What’s an amp? 

An amp is the basic unit of current, and the notation for the amp is the capital ‘A’. Compared to the circuits you are using with the BASIC Stamp, an amp is a very large amount of current. It’s a convenient value for describing the amount of current that a car battery supplies to headlights, the fan that cool a car’s engine, and other higher power
devices.

What’s Resistance?

 Resistance is the element in a circuit that slows down the flow of electrons (the current) from a battery’s negative terminal to its positive terminal. The ohm is the basic measurement of resistance. It has already been introduced and it’s abbreviated with the Greek letter omega (Ω).

What’s a Conductor?

 Copper wire has almost no resistance, and it’s called a conductor. 

Ground and/or reference 

are words you see used to refer to the negative terminal of a circuit. When it comes to the BASIC Stamp and Board of Education, Vss is considered the ground reference. It is zero volts, and if you are using a 9 V battery, it is that battery’s negative terminal. The battery’s positive terminal is 9 V. Vdd is 5 V (above the Vss reference of 0 V), and it is a special voltage made by a voltage regulator chip to supply the BASIC Stamp with power.

Ohm’s Law: V = I × R 

The voltage measured across a resistor’s terminals (V) equals the current passing through the resistor (I) times the resistor’s resistance (R).

Diode Forward Voltage: 

When an LED is emitting light, the voltage measured from anode to cathode will be around 1.6 V. Regardless of whether the current passing through it is a large or a small value, the voltage will continue to be approximately 1.6 V.

Kirchoff’s Voltage Law Simplified: 

voltage used equals voltage supplied. If you supply a circuit with 5 V, the number of volts all the parts use had better add up to 5 V.

Kirchoff’s Current Law Simplified: 

current in equals current out. The current that enters an LED circuit from Vdd is the same amount of current that leaves it through Vss. Also, if you connect three LED to the BASIC Stamp, and each LED circuit draws 5 mA, it means the BASIC Stamp has to supply all the circuits with a total of 15 mA.

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