Electricity

True or false: 1. ELECTRONS FLOW AT NEARLY THE SPEED OF LIGHT? 2. BATTERIES & GENERATORS CREATE ELECTRICITY? 3. ELECTRICITY LEAVES ONE BATTERY PLATE, THEN RETURNS TO THE OTHER? 5. TOO BAD FRANKLIN SAID ELECTRONS ARE NEGATIVE?

6. "ELECTRICITY" IS A PHENOMENON COMPOSED OF ENERGY? 7. ELECTRICITY IS MADE OF ELECTRONS? 8. STATIC ELECTRICITY IS THE OPPOSITE OF CURRENT ELECTRICITY? 9. EACH INDIVIDUAL ELECTRON CARRIES ENERGY?

10. ATOMS HAVE EQUAL NUMBERS OF ELECTRONS AND PROTONS? 11. CONDUCTORS ALLOW CHARGE TO PASS? 12. ELECTRICITY IS WEIGHTLESS? 14. "ELECTRICITY" IS A FORM OF ENERGY?

Law of Electric Charges: Like charges repel and opposites attract. Protons – positive Electrons- Negative Electric Force: The force between two charged objects Electric Field – force created by charged particles

Conductor - a material which contains movable electric charges Insulator – a material which doesn’t contain moveable electric charges Conductor - like a pipe which is already full of water Insulator - like a pipe with frozen liquid; a pipe plugged by ice

Conservation of charge: When you move electrons from one object to another they are neither created nor destroyed. Static electricity is the buildup of charges on an object. Electric discharge is the release of static electricity

Voltage Voltage- difference in charge between two area’s – Voltage is electric potential energy per unit charge, measured in joules per coulomb Charge flows from area’s of high voltage to low voltage Similar to the way water flow from high pressure to low

Resistance Resistance is the tendency of a material to resist the flow of electrons All materials offer some resistance – conductors offer less

Why light up? What qualities affect resistance? Think about a light bulb 1. Material – W 2. Thickness 3. Length 4. Temperature

The coulomb (C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity. A quantity of 1 C is equal to approximately 6.24 x 1018, or 6.24 quintillion. In terms of SI base units, the coulomb is the equivalent of one ampere-second. One coulomb is roughly equal to the amount of charge possessed by 6,000,000,000,000,000,000 (six billion billion) electrons. Just to give you an idea, one coulomb is roughly the amount of charge that flows through a 12-watt automotive light bulb in one second.

The Ampere Strikes Back or…Current The flow of electrons through wire is called current. Ampere or Amp- the amount of electric charge per second. “Electric energy” comes in the form of waves – which are bound to the electrons and protons in the wire The Ampere Strikes Back

Ohm – named after a dude – George Simon Ohm – if your cool he’ll be your “Ohmie” Ohm is a measure of resistance one ohm - one kilogram meter squared per second cubed per ampere squared (1 kg · m2 · s3 · A2). The ohm is also the equivalent of a volt per ampere (V/A).

Ohm’s law Ohm’s law V = I x R V = The voltage across a component I = The current going through a component R = The resistance of a component R = V/I or I = V/R

Electrical Calculations – What is Ohm’s Law? 3 V I = 1.5 amps I = 2 Ω

How are static charges detected?

DC – Direct Current – flows in one direction AC- Alternating Current – flows in both directions

What are batteries? Batteries are composed of a chemical substance which can generate voltage which can be used in a circuit. There are two kinds of batteries: dry cell and wet cell batteries. Below is an example of a dry cell. The zinc container of the dry cell contains a moist chemical paste surrounding a carbon rod suspended in the middle.

Wet cell batteries are most commonly associated with automobile batteries. A wet cell contains two connected plates made of different metals or metal compounds in a conducting solution. Most car batteries have a series of six cells, each containing lead and lead oxide in a sulfuric acid solution.

         Bulb 1            Bulb 2 The bulbs, batteries and wires in both figures are similar.  Will bulb 2 shine more, less, or equally brightly than bulb 1?       

What is the difference between an open circuit and a closed circuit? A closed circuit is one in which the pathway of the electrical current is complete and unbroken. An open circuit is one in which the pathway of the electrical current is broken. A switch is a device in the circuit in which the circuit can be closed (turned on) or open (turned off).

What are electric circuits? Circuits typically contain a voltage source, a wire conductor, and one or more devices which use the electrical energy. What is a series circuit? A series circuit is one which provides a single pathway for the current to flow. If the circuit breaks, all devices using the circuit will fail.

If the path is broken, no current flows through the circuit.

What is a parallel circuit? A parallel circuit has multiple pathways for the current to flow. If the circuit is broken the current may pass through other pathways and other devices will continue to work.

If one part of the path is removed, the current continues to flow through the other paths of the circuit.

How is household wiring arranged? Most household wiring is logically designed with a combination of parallel circuits. Electrical energy enters the home usually at a breaker box or fuse box and distributes the electricity through multiple circuits. A breaker box or fuse box is a safety feature which will open

How is Electrical Power calculated? Electrical Power is the product of the current (I) and the voltage (v) The unit for electrical power is the same as that for mechanical power in the previous chapter – the watt (W) Example Problem: How much power is used in a circuit which is 110 volts and has a current of 1.36 amps? P = I V Power = (1.36 amps) (110 V) = 150 W

How is electrical energy determined? Electrical energy is a measure of the amount of power used and the time of use. Electrical energy is the product of the power and the time. Example problem: E = P X time P = I V P = (2A) (120 V) = 240 W E = (240 W) (4 h) = 960Wh = 0.96 kWh

Electromagnetic Induction If magnet is moved quickly into a coil of wire, a current is induced in the wire. If the magnet is removed from the coil, a current is induced in the wire in the opposite direction By the same token, current can also be induced if the magnet stays put but the coil moves toward or away from the magnet Current is also induced if the coil rotates. In other words, it does not matter whether the magnet or the coil moves. It is the relative motion that counts.

What is magnetism? Magnetism is the properties and interactions of magnets The earliest magnets were found naturally in the mineral magnetite which is abundant the rock-type lodestone. These magnets were used by the ancient peoples as compasses to guide sailing vessels. Magnets produce magnetic forces and have magnetic field lines

Magnets have two ends or poles, called north and south poles Magnets have two ends or poles, called north and south poles. At the poles of a magnet, the magnetic field lines are closer together. Opposite poles of magnets attract each other and like poles of magnets repel.

The earth is like a giant magnet! The nickel iron core of the earth gives the earth a magnetic field much like a bar magnet.

What are magnetic domains? Magnetic substances like iron, cobalt, and nickel are composed of small areas where the groups of atoms are aligned like the poles of a magnet. These regions are called domains. All of the domains of a magnetic substance tend to align themselves in the same direction when placed in a magnetic field. These domains are typically composed of billions of atoms.

Electricity and Magnetism – how are they related? When an electric current passes through a wire a magnetic field is formed.

What is an electromagnet? When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.

What is a galvanometer? A galvanometer is an electromagnet that interacts with a permanent magnet. The stronger the electric current passing through the electromagnet, the more is interacts with the permanent magnet. Galvanometers are used as gauges in cars and many other applications. The greater the current passing through the wires, the stronger the galvanometer interacts with the permanent magnet.

Induced EMF It has been discovered by Oersted and company in early 19th century that Magnetic field can be produced by an electric current Magnetic field can exert force on electric charge So if you were scientists at that time, what would you wonder? An American scientist Joseph Henry and an English scientist Michael Faraday independently found that it was possible Though, Faraday was given the credit since he published his work before Henry did He also did a lot of detailed studies on magnetic induction

If you allow electrons to move through a wire, they will create a magnetic field around the wire. Similarly, if you move a magnet near a wire, the magnetic field will cause electrons in the wire to move. A generator is a simple device that moves a magnet near a wire to create a steady flow of electrons.

Electric Generators Faraday’s law of induction What does a generator do? Transforms mechanical energy into the electrical energy What does this look like? An inverse of an electric motor which transforms electrical energy to mechanical energy Faraday’s law of induction

Generator is motor run backwards Motor, generator parts are almost all the same. Input and output are reversed. Apply mechanical energy to rotor (e.g. turn it by hand), and voltage is generated in coil.