1. 1 Chapter Three Electrical Concepts & Components

2. 2 Basic Units & Dimensions  Fundamental quantities are: Mass, Length, Time, Charge  System of Units: MKS or SI units.  MKS = meter, kilogram, second.  The basic unit of charge is the coulomb.  In MKS system uses the basic units or some designated power of ten of those units.

3. 3 Basic Units & Dimensions  All given non-SI units should be converted into SI units before solving a problem, this is done using a table of conversion factors.  Each of the basic units has a “ dimension ” associated with it regardless of whether SI or non-SI units are used to measure it.  All the quantities have a unique dimension which is a combination of the four basic dimensions.  All conversion factors must be dimensionless quantities.

4. 4 Energy & Power  Law of conservation of energy: energy cannot be created or destroyed in non nuclear situation, but it may be converted into other forms of energy.  The basic unit of energy in the SI system is the Joule.  Power is the time rate at which energy is expended. Power=energy/time.  The basic unit of power in British system is horse power, and in the SI system Watt.

5. 5 Charge & Current  The electric charge on a single electron has a charge e= -1.602x10 -19 C.  Charge can neither be created nor destroyed.  Electrical current: the amount of charge passing a given point in a fixed instant of time. I= q/t.  1 A(ampere) = is a one coulomb of charge passing in one second.  Current is measured using an ammeter.

6. 6 Voltage  Coulombs law: gives the force exerted by one charge on another charge.  Voltage: is the amount of energy required to bring a test charge up to specific point near another charge divided by the value of the test charge.

7. 7 Voltage  The voltage is measured in Volts.  Direct current or DC voltage means a voltage that does not vary with time.  Alternating current or AC voltage which means a voltage that varies sinusoidally in time, going through a positive & negative peak each cycle.

8. 8 Electrical Power & Energy  Power = Voltage x Current (measured in Watt)  1 Watt = is the power when a voltage of one volt is across a device that has a current of one ampere flowing through it.  1 horse power = 1 hp = 746 W.  Energy = power x time (measured in joules)

9. 9 Passive Electric Component Electric Components: 1.Passive: means that the device itself needs no external electrical power source in order to operate.(e.g. Resistor, capacitor, & Inductor) 2.Active: means that the device requires electrical power source in order to function. (e.g. vacuum tubes, transistor)

10. 10 Resistor  Resistance is measured in ohms (Ω ).   Ohms law: the voltage and the current in a given resistance are linearly related. V= I.R (R= resistance) P = V.I = V 2 /R = I 2.R

11. 11 Capacitor  Capacitor: is two conductors separated by dielectric material, which have a voltage difference between them & have charges of different polarities on the two conductor.  C = Q / V  Capacitance is measured in Farad (1F is the capacitance of one coulomb of charge on each conductor with a voltage difference 1V)

12. 12 Capacitor  Capacitor doesn ’ t provide a conducting path between the two plates. i.e. It blocks DC current.  If the voltage across C is varying with time, time-varying current can be carried through C.

13. 13 Inductor  A magnetic field is produced when a current flow through a wire.  Magnetic flux: is the product of the area through which the magnetic field lines are flowing times the magnetic properties of the material (permeability).  Inductance(measured in Henry): is the ratio of the total magnetic flux linked by the current producing it to the current.