Understanding Ohm's Law, Coulomb's Law, Electric Power & Generators

1. Presentationon Ohm’s Law, Coulomb’s Low, Electric Power & Generators Continued

2. Ohm’s Law

3. Definition Ohm’s law state that, temperature remaining constant, the current passing through a conductor directly proportional to the potential difference or voltage across it. This means IαV

4. OHM'S LAW I = V/R, I = current, V = voltage, and R = resistance *Depending on what you are trying to solve we can rearrange it two other ways. V = I x R R = V/I *All of these variations of Ohm’s Law are mathematically equal to one another.

5. History George Simon Ohm 1826 George Simon Ohm (1787-1854) wanted to measure the motive force of electrical currents. He found that some conductors worked better than others and quantified the differences. He waited quite some time to announce "Ohm's Law" because his theory was not accepted by his peers. The unit for resistance is named after him.

6. Relationship between P,E,I &R Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.

7. Relationship between P,E,I &R ( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps. ( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts. ( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms. ( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

8. Coulomb's Law

9. Definition Two point charges attract or repel each other by a force, which is directly proportional to the product of the magnitude of their charges & inversely proportional to the square of distance between them. The direction of the force depends on the electrical sign of the charge.

10. Coulomb's Law If two point charges Q1 & Q2are separated in a medium by a distance d, then the electrostatic force F between this two charges is given by:- FαQ1*Q2 Fα1/d2 So, combining the above two equation we can write FαQ1*Q2/d2 or F=k Q1*Q2/d2 Here, K is the proportional constant. The value of K is depends on the system of unit. In SI system the unit of F is Newton, unit of charge is coulomb & unit of distance is meter. In this system the unit of K in free space is, K=1/4лє0=9*109 Nm2c2

11. Using Coulomb’s Law 1. Coulomb’s Law applies only to point charges. (This is particularly important because charge tends to move around on conductors.) 2. Strictly speaking, Coulomb’s Law applies only to electrostatics (non-moving charges). (However, it is usually OK provided v<c). 3. Electrostatic forces, like other forces, can be superimposed.

13. Definition Electric power is the product of electric current and voltage.Itis defined as the rate at which electricalenergy is transferred by an electric circuit

14. Continued....... P=power in watt T=time in hour The SI unit of power is watt. • The electric power in watts associated with a complete electric circuit or a circuit component represents the rate at which energy is converted from the electrical energy of the moving charges to some other form, e.g., heat, mechanical energy, or energy stored in electric fields or magnetic fields. For a resistor in a D C Circuit the power is given by the product of applied voltage and the electric current P = VI Power = Voltage x Current

15. How electric power work When electric current flows in a circuit, it can transfer energy to do mechanical or thermodynamic work. Devices convert electrical energy into many useful forms, such as heat (electric heaters), light (light bulbs), motion (electric motors), sound (loudspeaker) or chemical changes. Electricity can be produced mechanically by generation, or chemically, or by direct conversion from light in photovoltaic cells, also it can be stored chemically in batteries.

16. Generators

17. Definition Basically speaking, a generator is a device which uses a magnet in order to induce a flow of electric current in a circuit, much like how a water pump pushes water through a hose. A electrical generator is a device that convents mechanical energy to electrical energy, generally using electromagnetic induction.

18. How generator work A generator functions because of the relation between magnetism and electricity. If electrons (the parts of an atom which carry a negative charge) move through something conductive like a wire, they generate a magnetic field. Conversely, if a magnetic field is placed near a wire and moved, its motion causes the electrons in the wire to move because of a change in electrical potential. This is known as a current.

19. History In the 1830s, Michael Faraday discovered this principle and built the first electromagnetic generator known as the Faraday disc, which used a copper disc rotating between the poles of a horseshoe magnet. In 1832, the first dynamo was built consisting of a power-producing armature moving within a stationary magnetic field.

20. Importance Today, we are very dependent on a steady power supply. The use of electrical devices like refrigerators and computers means we can't go without power for very long or there will be serious consequences. Even so, power outages still occur. The one the US experienced in 2003 affected over 60 million people and was the largest outage to occur in US history. California recently experienced a wave of rolling blackouts. A New Orleans without power descended in chaos in the wake of Hurricane Katrina.

21. Types of Generators Generators types describes into two ways Based on output current Based on structure

22. Based on output current • AC Generators • DC Generators • AC Generators • This type of generators generates in alternatives current that means the direction of current changes with time & the shape of current flow the sign wave. • DC Generators • This type of generators generates in direct current that means the direction of current is not changes with time & the shape of current flow the unidirectional wave like a line.

23. Based on structure Standby generators Portable generators Commercial generators

24. Based on structure Standby generators These are large, often permanent units that are stationed outside a home, office building, warehouse, shopping mall, and the like to provide backup power in case the mains electricity switches off. These sets are plugged into the main electric lines and can sense when a power interruption has occurred. They automatically start and provide emergency power generating a few seconds after coming online.

25. Based on structure Portable generators These are designed to be transported whether on a cart, trailer or by hand to provide power where there is no utility power supply, as in campsites and construction sites. Their output is sufficient to run appliances such as pumps, refrigerators, lights, radios, and televisions, and the larger ones can be used to power sound systems, high-intensity lights and parked aircraft. The smaller generators typically use gasoline as fuel, whereas the larger ones, capable of providing up to 1,000 kilowatts or more of electricity

26. Based on structure Commercial generators In areas where the power supply is intermittent or lacking as in Third World provincial areas, generators can also be set up to provide additional power.