1 An Introduction to Electronics by William O’Shaughnessy

2 An Introduction to Electronics Electronics is the study of the flow of electrons in an electronic circuit made of electronic components connected in a closed path. An electronic component is something that affects the flow electrons, by resisting their flow, creating potentials, or storing them.

3 An Introduction to Electronics The flow of electrons is called a current Its mathematical symbol is “I”. The unit of current flow is the Ampere, very commonly abbreviated as Amp. An Amp is the flow of 6.24 * 10^18 electrons past a point in one second.

4 An Introduction to Electronics Two Things are needed to create a current flow a source of electrical potential and a path for the electrons to flow through Consider filling this room with water with the doors sealed. (The water is the electrons) It can not leave the room without a hole in the floor. That hole is the path for the water to flow.

5 An Introduction to Electronics Consider filling this room with water with the doors sealed. (The water is the electrons) It can not leave the room without a hole in the floor. That hole is the path for the water to flow. How fast the water hits the next floors is determined by the height between floors. This is called potential or voltage in electricity.

6 An Introduction to Electronics Two Kinds of Current Direct Current: Flows only one way Alternating Current: First flows one way and then the opposite direction How often current changes its direction in one second is called its frequency. The unit of frequency is the Hertz Abbreviated Hz = cycles per sec Wall Current 60 Hz at 120 volts

7 An Introduction to Electronics So we have the two most important characteristics of electronics and the movement of electrons: 1.) Current: how many are flowing 2.) Voltage: how fast they are moving or how fast they could move.

8 Electronic Components The Battery A battery produces electronic potential by chemical reactions for example: Lead Acid or Lithium Ion A battery's greatest potential is called its voltage It produces Direct Current How many electrons it can put out is called its Amp*hour rating

9 Electronic Components The Resistor The resistor is a conductor of electrons A wire is a resistor with a very low resistance The unit of resistance is Ohms,  Its units symbol is  Its math symbol is R

10 Electronic Components The Resistor A conductor can be thought of as a pipe The resistance of a wire could be about.1 ohms; this could be thought of as a 10 inch diameter pipe A resistor of 100 ohms would be like a pipe of.01 inches diameter

11 Electronic Components The Resistor The voltage across a resistor is proportional the amount of current that is passing through it. V = IR This is Ohm's Law. It is the most important Law of Electronics Resistors do not generate potential Resistors give off heat when they pass current Pwr = V*I = I^2 R

12 Electronic Components The Capacitor A Capacitor is a circuit element that stores charge, that is electrons. A capacitor can generate potential. That potential is proportional to the charge in the capacitor. Will accept charge until its potential equals the potential of the source A capacitor will not pass DC current It will pass Alternating Current

13 Electronic Components The Capacitor A Capacitor can pass AC current Small capacitors act as resistors with high values to AC current. Its resistance to AC is 1/(2  F C) Where F is the Frequency of the AC The unit of capacitance is the Farad A capacitor of 1 Farad is almost a battery. Micro nano pico More common 1uf, 1nf, 1pf

14 Electronic Components The Inductor Is coil of wire around an iron core or air The inductance, symbol L, is proportional to the square of the number of turns of wire Its resistance to AC is 2  F L Where F is the Frequency of the AC The unit of inductance is the Henry Common sizes are milli Henries(mH), microHenries(uH), and nanoHenries(nH)

15 Electronic Components L C Summary Capacitors in parallel with a voltage source oppose any change in its potential. In series capacitors pass AC but not DC. Inductors in series with a current source oppose any change in its current. They pass DC and AC but they delay and oppose any change in current.

16 Electronic Components The Transformer Is two inductors wound around the same core Is used to multiply an AC voltage by the ratio of the turns in the two inductors. If 120 VAC is applied to 4 turns, 60 VAC comes out of the two turns If 120 VAC is applied to 2 turns, 240 VAC comes out of the 4 turns The coil that gets the voltage is called the “primary” The other coil is called the “secondary” Is the primary component in a Wall Wart (formal name Power Adapter) And the biggest thing on an electrical pole.

17 Electronic Components The Diode Is a semiconductor circuit element that will pass current only in one direction. Electrical current flows in the direction of the arrow, electrons flow in the direction opposite the arrow. Is the second major component of a Wall Wart; the third is a capacitor. The wire with the bar is the Cathode The wire with the arrow is the Anode

18 Electronic Components The Diode Is a semiconductor circuit element that will pass current only in one direction. Electrical current flow in the direction of the arrow, electrons flow in the direction opposite the arrow. Is the second major component of a Wall Wart; the third is a capacitor. The wire with the bar is the Cathode The wire with the arrow is the Anode

19 Electronic Components Bipolar Transistor Is a semiconductor circuit element that amplifies the base to emitter current. The bar is the base, the arrow is the emitter, the line is collector The amplified current flows from the collector to the emitter in an NPN and from the emitter to the collector in a PNP transistor. The amplification factor is called the Beta or h npn pnp

20 Electronic Components Field Effect Transistor Is a semiconductor circuit element that switches a current with a voltage The current goes from a Drain to a Source (electrons from the Source to the Drain) Take very, very little current to turn on They are said to have a high impedance input n-channel p-channel

21 Rules of Using a Multimeter Never measure current without the instructors permission (A or ma) Never measure resistance in a powered on circuit Don't touch the metal part of the probe when measuring in a circuit. Always measure voltages starting with the highest scale and work down to smaller scales

22 Soldering Always assume all metal parts of a soldering iron are hot. First rule of soldering: get the connection hot before applying solder. (Now obsolete) New rule: nothing conducts heat like liquid metal. Have a little liquid solder on the tip of you soldering iron and use it and contact pressure to transfer heat from your iron to the connection before applying solder. Besure you see solder flow onto the components. Keep the iron over the bench.