1. م / محمد عبدالله الزبيدي الأنظمة الكهروميكانيكية

2. Introduction to Electricity Fundamentals of Electricity The Types Of Conductors Charge Current Voltage Resistance

3. The International System of Units SymbolUnitQuantity MMatterLength KgKilogramMass SSecondTime AAmpereCurrent KKelvinTemperature CdCandleLuminous Intensity

4. The SI Prefixes SymbolPrefixPower Of Ten TTera1*10^12 GGiga1*10^9 MMega1*10^6 KKilo1*10^3 mMilli1*10^-3 μ Micro1*10^-6 NNano1*10^-9 PPico1*10^-12

5. Atoms Atoms consist of even smaller particles called protons, neutrons and electrons The nucleus of the atom contains protons, which have a positive charge, and neutrons, which have no charge and Electrons have a negative charge.

6. Electricity Is the flow of electrons from one atom to another.

7. The Types Of Conductors Conductors :- electron flow easily (Low Resistance ) as Copper, Silver and Aluminum. Semi – Conductors :- electron flow with some difficult ( Medium Resistance ) as Carbon, germanium and Silicon. Insulators :- electron flow with great difficult ( High Resistance ) as Rubber, glass and porcelain

8. Fundamentals of Electricity Charge ( symbol Q) Current (symbol I) Voltage (symbol E or V) Resistance (symbol R)

9. Charge Measured in Coulomb ( symbol C) Electron (e) = 1.602*10^-19 c Example :- How Much Charge represented By 4600 electron. Sol/ Q= -1.602*10^-19 * 4600 = -7.4*10^-16 c

10. Current The flow of free electrons in the same general direction from atom to atom,it is measured in amperes (“amps” or “A”). I = dQ/dt, Q= Example:Q= 5t*sin4 π t mc, calculate the current at t=0.5 second Sol/ I = dQ/dt =d(5t*sin4 π t)/dt = 5sin4 π t + 5t*cos4 π t *4 π = 5sin4 π t + 20t*cos4 π t at t= 0.5 = 10 π mA

11. Example :- Determine Q between t=1 sec and t=0.5 sec if I = ( 3t^2 – t ) A Sol/ Q= = [ t^3 – 0.5t^2 ] = =[(3t^3/3) –(t^2/2)] =[ 8 – (0.5*4)] – [ 1 – 0.5 ] =6 – 0.5 = 11/2 = 5.5 c

12. Voltage Voltage is the force that is applied to a conductor to free electrons, which causes electrical current to flow. It is measured in volts or “V”. There are two methods that voltage forces current to flow: Direct Current Alternating Current

13. Direct current (DC) : With this method, the voltage forces the electrons to flow continuously in one direction through a closed circuit. Batteries and DC generators produce DC voltage. Alternating current (AC) : With this method, voltage forces electrons to flow first in one direction, then in the opposite direction, alternating very quickly. A generator is used to produce AC voltage. Factories, our home and offices.

15. Resistance The restriction to the flow of electrons through a conductor is called resistance and it is measured in ohms ( Ω )

16. In general, there are four factors that affect the amount of resistance in a conductor :- Material Length Cross-Sectional Area Temperature

18. Length: The longer the conductor, the more resistance in the conductor. Resistance is increased or decreased in proportion to the conductor’s length. For example, a 2-foot long conductor would have twice the resistance of a one-foot long conductor

19. Cross-Sectional Area: As the cross-sectional area of a conductor increases, the resistance decreases, and vice versa. For example, if the area of a conductor is doubled, the resistance is cut in half.

20. Temperature: Usually when the temperature of a conductor increases, the resistance increases. R = ρ * L / A Where : R : Resistance ( Ω ) ρ : Resistivity ( Ω m) Length ( m ) L : A :Cross-section Area ( m^2)