Electricity, Components and Circuits

1. Electricity, Components and Circuits Technician’s guide to understanding electrical aspects of ham radio Presented by dan Lundwall, n7xdl Murray amateur radio club

2. ELECTRICITY • Although radios use sophisticated electronics, they are based on fundamental principles of electricity. • In this presentation you will learn the following: • Voltage & Current • Circuits • Resistance (which, buy the way, is futile!) • Watts (Power baby!) • AC / DC • Common types of Electronic Components

3. ELECTRICITY: Voltage & Current • VOLTAGE (represented by the symbol E or e) is the electromotive force or electric potential that makes electrons move. • Voltage is measured in units of volts which is abbreviated as V or v. • Voltage is always measured from one point to another or with respect to some reference voltage. • Voltage is measured with a voltmeter. • The polarityof voltage can be either positive or negative. A negative voltage repels electrons and a positive voltage attracts them. • The Earth’s surface acts as a universal reference for voltage measurements and is called earth ground, ground potential, ground, or earth.

4. ELECTRICITY: Voltage & Current • Electric CURRENT (represented by the symbol I or i) is the flow of electrons. • Electrons are negatively charged atomic particles. • Current is measured in units of amperes, which is abbreviated as A or amps. • Current is always measured as the flow through something, such as a wire or electronic component. • An ammeter is used to measure current. • Electrons are so small that to light a household 100-watt bulb with a current of 1 ampere, 6.25 billion billion of them must pass through the bulb each second! That quantity, 6,250,000,000,000,000,000 or 6.25 x 1018 electrons, make up one coulomb of electric charge.One ampere is the flow of one coulomb of electrons per second.

5. ELECTRICITY: Circuits • A CIRCUIT is any path through which current can flow. • If two or more devices, such as light bulbs are connected in a circuit so that the same current must flow through all of them, that is a series circuit. If two or more are connected so that the same voltage is present across all of them, that is a parallelcircuit.

6. ELECTRICITY: Resistance • All materials impede the flow of electrons to some degree. This property is called RESISTANCE, represented by the symbol R. • Resistance is measured in ohms, which are represented by the Greek letter omega, Ω. • Resistance is measured with an ohmmeter. • Materials in which electrons flow easily in response to an applied voltage are called conductors. Metals such as copper are good conductors, and so is salt water. • The human body conducts electricity very well! • Materials that resist or prevent the flow of electrons are insulators, such as glass and ceramics, dry wood and paper, and most plastics and other non-metals.

7. ELECTRICITY: Ohm’s Law • Georg Ohm, a 19th century scientist, discovered that voltage, current and resistance are proportional to each other. • Ohm’s Law states that current is directly proportional to voltage, and inversely proportional to resistance. The more a material resists the flow of electrons, the lower the current will be in response to voltage across the material. • As an equation, this is stated as I = E / R. • If you know any two of I, E, or R, you can determine the missing quantity as follows: • R = E / II = E / R E = I x R

8. ELECTRICITY: Ohm’s Law

9. ELECTRICITY: Ohm’s Law

10. ELECTRICITY: Ohm’s Law TO FIND Voltage: Amperes x Resistance Amperes: Voltage / Resistance Resistance: Voltage / Amperes

11. ELECTRICITY: Watts (Power) • POWER, represented by the symbol P, is measured in watts which are abbreviated as W. • Power is the rate at which electrical energy is used. • Power is calculated as the product of voltage and current. • An amount of power consumed is often referred to as the load that is applied to a circuit. • As with Ohm’s Law, if you know any two of P, E or I, you can determine the missing quantity. • P = E x I E = P / I I = P / E • Look familiar?

12. ELECTRICITY: Watts (Power) Watts = Amps x Volts Amps = Watts / Volts Volts = Watts / Amps

13. Putting it all together…

14. ELECTRICITY: AC and DC • NO… we are not talking about the rock band AC/DC! • AC (alternating current) and DC (direct current) • Electrical current takes different forms, depending on the source that creates the voltage making the electrons move. • Current that flows in one direction all the time is direct current, abbreviated dc. • Current that regularly reverses direction is alternating current, abbreviated ac. • Just like current, a voltage that has the same polarity (the same direction from positive to negative voltage) all the time is dc voltage. A voltage that regularly reverses polarity is an ac voltage. • Let’s look at the differences on a scope…

15. COMMON ELECTRICAL COMPONENTS • RESISTOR

16. COMMON ELECTRICAL COMPONENTS • RESISTOR Color Code

17. COMMON ELECTRICAL COMPONENTS • RESISTOR Symbol

18. COMMON ELECTRICAL COMPONENTS

19. COMMON ELECTRICAL COMPONENTS

20. COMMON ELECTRICAL COMPONENTS • CAPACITOR

21. COMMON ELECTRICAL COMPONENTS • A CAPACITOR store electrical energy in the electric field created by a voltage between two conducting surfaces (such as metal foil) called electrodes separated by in insulating dielectric. • Storing energy this way is called capacitance and it is measured in farads (F). • Capacitors used in radio circuits have values measured in picofarads (pF), nanofarads (nF) and microfarads (μF). • As it stores and releases energy in a circuit, a capacitor smoothes out voltage changes.

22. COMMON ELECTRICAL COMPONENTS • CAPACITOR Symbol

23. COMMON ELECTRICAL COMPONENTS • INDUCTORS

24. COMMON ELECTRICAL COMPONENTS • An INDUCTOR stores magnetic energy in the magnetic field created by current flowing through a wire. • This property is called inductance and it is measured in henrys (H). • As it relates to radio circuits, inductor values are measured in nano-henrys (nH), micro-henrys (μH), milli-henrys (mH) and henrys (H). • Inductors are made from wire wound in a coil, sometimes around a core of magnetic material that concentrates the magnetic energy.

25. COMMON ELECTRICAL COMPONENTS • INDUCTOR symbol

26. COMMON ELECTRICAL COMPONENTS TRANSFORMER

27. COMMON ELECTRICAL COMPONENTS TRANSFORMERS are made from two or more inductors that share their stored energy. This allows energy to be transferred from one inductor to another while changing the combination of voltage and current. For example, a transformer is used to transfer energy from a homes 120 VAC outlet to a lower voltage for use in electronic equipment… say, a door bell.

28. COMMON ELECTRICAL COMPONENTS TRANSFORMER symbol

29. COMMON ELECTRICAL COMPONENTS DIODES

30. COMMON ELECTRICAL COMPONENTS DIODES, TRANSISTORS AND INTEGRATED CIRCUITS Resisters, capacitors and inductors generally treat all values and polarities of voltage and current the same. There are other types of components whose response depends on the polarity and value of voltage and current. These are usually constructed from a semiconductor material. Some materials don’t conduct electricity quite as well as a metallic conductor, nor are they a good insulator. These materials are called semiconductors. Some semiconductors, such as silicon, have the useful property that adding small amounts of certain impurities, called doping, changes their ability to conduct current. The impurities create N-type or P-type material, depending on the chemical properties of the impurity. When N- and P-type material are placed in contact with each other, the result is a PN junction that conducts better in one direction than the other! This and other properties are used to create many useful electronic components, generally referred to as semiconductors.

31. COMMON ELECTRICAL COMPONENTS DIODES, TRANSISTORS AND INTEGRATED CIRCUITS

32. COMMON ELECTRICAL COMPONENTS DIODES, TRANSISTORS AND INTEGRATED CIRCUITS A semiconductor that only allows current flow in one direction is called a diode. A diode has two electrodes, an anode and a cathode. The cathode is usually identified by a stripe. A special type of diode, the light-emitting diode or LED, gives off light when current flows through it. The material from which the LED is made determines the color of light emitted. LED’s are most often used as visual indicators.

33. COMMON ELECTRICAL COMPONENTS DIODES, TRANSISTORS AND INTEGRATED CIRCUITS Transistors are components made from patterns of N- and P-type material. The patterns form structures that allow the transistor to use small voltages and currents to control larger ones. With the appropriate external circuit and a source of power, transistors can amplify or switch voltages and currents. Using small signals to control larger signals is called gain. There are two common tyhpes of transistors: bipolar junction transistors (BJT) and field-effect transistors (FET). The BJT is made from three alternating layers of N- and P-type material. The electrodes are called the base, emitter and collector. The gate electrode on a FET transistor is used to control current flow through the channel.

34. COMMON ELECTRICAL COMPONENTS DIODES, TRANSISTORS AND INTEGRATED CIRCUITS An INTEGRATED CIRCUIT (IC or chip) is made of many components connected together as a useful circuit and packaged as a single component. IC’s range from very simple circuits consisting of a few diodes all the way to complex microprocessors or signal-processing chips with many thousands (sometimes millions) of components.

35. ELECTRICAL UNITS