Subatomic

1. Topic 1ELECTRONIC PRINCIPLES1.1Basic Electronic PrinciplesLECTURER NAME: MR. KHAIRUL AKMAL BIN NUSI

2. Subatomic

3. An atom is the basic component of a chemical element, but atoms themselves are composed of various combinations of smaller, or subatomic, particles, such as electrons, protons, and neutrons.

4. Nucleus Protons A proton is a subatomic particle with a positive charge equivalent to the negative electrical charge of an electron. Protons and neutrons together form the nucleus of an atom. The number of protons in a nucleus determine the 'atomic number' of the element – the atomic number of hydrogen is 1; carbon has 6 protons so its atomic number is 6; iron has 26 protons, so its atomic number is 26, and so on. • At the center of every atom is a nucleus, comprised of a number of protons and (with the exception of hydrogen) neutrons. The simplest and lightest chemical element is hydrogen, which has a nucleus containing just one proton and no neutrons. Each distinct chemical element has a unique number of protons, coupled with a number of neutrons, which can vary.

5. Neutrons Electrons An electron is a subatomic particle with a negative electrical charge. Electrons orbit around and exist outside of the nucleus of an atom. They are bound to the atom by electromagnetic forces, but they are very light and can move between atoms creating an electrical current. All electrical and electronic activity is created by moving electrons. As they form the outer shell or shells of an atom, electrons are largely responsible for how chemicals interact with each other. • A neutron is subatomic particle similar in mass to a proton, with no electrical charge. The number of neutrons in a nucleus determines the isotope, or particular form, of the element. For instance, iodine 127 and iodine 131 are both forms of iodine, with the same atomic number and the same number of protons, but with different numbers of neutrons and therefore different atomic weights.

6. 1a) Charged particles in matter :- Atoms have three types of sub atomic particles. They are electrons, protons and neutrons. Electrons are negatively charged (e-), protons are positively charged (p+) and neutrons have no charge (n). The mass of an electron is 1/2000 the mass of a hydrogen atom. The mass of a proton is equal to the mass of a hydrogen atom and is taken as 1 unit. The mass of a neutron is equal to the mass of a hydrogen atom and is and is taken as 1 unit. b) Discovery of sub atomic particles :- In 1900, J.J.Thomson discovered the presence of the negatively charged particles called electrons in the atom. In 1886, E.Goldstein discovered new radiations in gas discharge and called them canal rays. These rays were positively charged. This later led to the discovery of the positively charged particles called protons in the atom. In 1932 Chadwick discovered the presence of particles having no charge in the atom called neutrons.

7. 2) Structure of an atom :- a) Thomson’s model of an atom :- According to Thomson an atom is similar to a Christmas pudding. The pudding had positive charge and the electrons having negative charge were like plums on the pudding. He proposed that :- i) An atom consists of a positively charged sphere and the electrons are embedded in it. ii) The negative and positive charges are equal in magnitude So the atom as a whole is electrically neutral.

8. b) Rutherford’s model of an atom :- Rutherford’s alpha scattering experiment :- Rutherford allowed a beam of fast moving alpha particles ( α – particles) having positive charge to fall on a thin gold foil. He observed that :- i) Most of the α – particles passed straight through the gold foil. ii) Some of the α – particles were slightly deflected by small angles. iii) Very few α – particles appeared to rebound.

9. Conclusions from Rutherford’s alpha scattering experiment :- i) Most of the space inside an atom is empty. (because most of the α – particles passed straight through the gold foil.) ii) The atom had a small nucleus having positive charge. ( because some of the α – particles having positive charge were slightly deflected by small angles.) iii) The size of the nucleus is very small compared to the size of the atom. (because very few α – particles appeared to rebound and most of the positive charge and mass of the atom is in the nucleus.) Rutherford’s model of an atom :- i) An atom has a positively charged nucleus at its centre and most of the mass of the atom is in the nucleus. ii) The electrons revolve around the nucleus in different orbits. iii) The size of the nucleus is very small compared to the size of the atom.

10. Defects of Rutherford’s model of the atom :- Rutherford’s model of an atom Negatively charged electron - Any particle in a circular orbit would undergo acceleration and during acceleration the charged particle would radiate energy. So the revolving electrons would lose energy and fall into the nucleus and the atom would be unstable. We know that atoms are stable. Negatively charged electrons in orbits around the nucleus - + - Very small positively charged nucleus Positively charged nucleus

11. c) Bohr’s model of an atom :- Shells or energy levels in an atom i)An atom has a positively charged nucleus at its centre and most of the mass of the atom is in the nucleus. ii) The electrons revolve around the nucleus in special orbits called discrete orbits. iii) These orbits are called shells or energy levels and are represented by the letters K, L, M, N etc. or numbered as 1, 2, 3, 4, etc. iv) While revolving in the discrete orbits the electrons do not radiate energy.

12. 3) Distribution of electrons in different shells :- The distribution of electrons in the different shells was suggested by Bhor and Bury. The following are the rules for filling electrons in the different shells. i) The maximum number of electrons in a shell is given by the formula 2n2 where n is the number of the shell 1, 2, 3 etc. First shell or K shell can have = 2n2 = 2 x 12 = 2x1x1 = 2 electrons Second shell or L shell can have = 2n2 = 2 x 22 = 2x2x2 = 8 electrons Third shell or M shell can have = 2n2 =2 x 32 = 2x3x3 = 18 electrons Fourth shell or N shellcan have = 2n2 =2 x 42 = 2x4x4 = 32 electrons and so on. ii) The maximum number of electrons that can be filled in the outermost shell is 8. iii) Electrons cannot be filled in a shell unless the inner shells are filled.

13. Composition of the atoms of the first eighteen elements :-

14. Atomic structure of the first eighteen elements :- H He N Li Be B C O Ne F Na Mg Si P S Cl Al Ar

15. 4) Valency:- Valency is the combining capacity of an atom of an element. The electrons present in the outermost shell of an atom are called valence electrons. If an atom’s outermost shell is completely filled, they are inert or least reactive and their combining capacity or valency is zero. Of the inert elements Helium atom has 2 electrons in the outermost shell and the atoms of other elements have 8 electrons in their outermost shell. Atoms having 8 electrons in their outermost shell is having octet configuration and are stable. If an atom’s outermost shell is not completely filled it is not stable. It will try to attain stability by losing, gaining or sharing electrons with other atoms to attain octet configuration. The number of electrons lost, gained or shared by an atom to attain octet configuration is the combining capacity or valency of the element Eg :- Hydrogen, Lithium, Sodium atoms can easily lose 1 electron and become stable. So their valency is 1. Magnesium can easily lose 2 electrons. So its valency is 2. Aluminiun can easily lose 3 electrons. So its valency is 3. Carbon shares 4 electrons. So its valency is 4. Fluorine can easily gain 1 electron and become stable. So its valency is 1. Oxygen can easily gain 2 electrons. So its valency is 2. Nitrogen can easily gain 3 electrons. So its valency is 3.

16. 5) Atomic number and Mass number :- a) Atomic number (Z) :- The atomic number of an element is the number of protons present in the nucleus of the atom of the element. All the atoms of an element have the same atomic number. Eg :- Hydrogen – Atomic number = 1 (1 proton) Helium - Atomic number = 2 (2 protons) Lithium - Atomic number = 3 (3 protons) b) Mass number (A) :- The mass number of an element is the sum of the number of protons and neutrons (nucleons) present in the nucleus of an atom of the element. The mass of an atom is mainly the mass of the protons and neutrons in the nucleus of the atom. Eg :- Carbon – Mass number = 12 (6 protons + 6 neutrons) Mass = 12u Aluminium – Mass number = 27 (13 protons + 14 neutrons) Mass = 27u Sulphur – Mass number = 32 (16 protons + 16 neutrons) Mass = 32u In the notation of an atom the Mass number atomic number and mass number Eg :- N are written as :- Atomic number Symbol of element 14 7

17. 5) Isotopes :- 1 2 3 1 1 1 12 14 6 Isotopesare atoms of the same element having the same atomic numbers but different mass numbers. Eg :- Hydrogen has three isotopes. They are Protium, Deuterium (D) and Tritium (T). H H H Protium Deuterium Tritium Carbon has two isotopes. They are :- C C Chlorine has two isotopes They are :- Cl Cl 6 35 37 17 17

18. 6) Isobars :- 40 40 Ca Ar 20 Isobars are atoms of different elements having different atomic numbers but same mass numbers. These pairs of elements have the same number of nucleons. Eg :- Calcium (Ca) – atomic number - 20 and Argon (Ar) – atomic number 18 have different atomic numbers but have the same mass numbers – 40. Iron (Fe) and Nickel (Ni) have different atomic numbers but have the same atomic mass numbers – 58. 18 58 58 Ni Fe 26 27

19. Electronic • Electronics is the branch of physics, engineering and technology dealing with electrical circuits that involve active electrical components such as vacuum tubes, transistors,diodes and integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible and is usually applied to information and signal processing. Similarly, the ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a working system.

20. Faraday Basics • Faraday's law of induction is one of the important concepts of electricity. It looks at the way changingmagnetic fields can cause current to flow in wires. Basically, it is a formula/concept that describes how potential difference (voltage difference) is created and how much is created. It's a huge concept to understand that the changing of a magnetic field can create voltage

21. Stepper motor • A stepper motor is a brushless, synchronous electric motor that converts digital pulses into mechanical shaft rotation. Every revolution of the stepper motor is divided into a discrete number of steps, in many cases 200 steps, and the motor must be sent a separate pulse for each step. • Types of Step Motors • There are three basic types of step motors: variable reluctance, permanent magnet, and hybrid.

23. Stepper motor are designed to rotate in a number of precisely defined steps. • The number of steps per revolution are defined by the number of magnetic poles in the motor • They usually controlled by a microprocessor electronically switching a set of stationary electromagnets. • Stepper motors are used in automotive for applications such as instrument panel controls and air conditioner controls.

24. 1.2 Understand the operation principle of the free electron

25. Electrical current • Current refers to the electrons passing any given point in the circuit in one second. Its flow on a wire or conductor, measured in amperes or amps. Electrical current is like the rate that water flows through a pipe. If there is a large volume of water to flow, a big pipe is needed. • Current will increased as pressure or voltage is increased-provided circuit resistance remains constant.

26. voltage • For electric current to flow, the electrons need a complete pathway, or circuit. To make them move, there must be a force. It is called electromotive force or EMF, also known as voltage. • The larger the charge at the positive terminal, the more strongly it attracts free electrons. This attraction acts as a force driving the electrons along. The greater the force, the stronger the electrical current.

28. Resistance • The ohm is the resistance of a conductor such that a constant current of 1 ampere in it produces a voltage of 1 volt between its ends.

29. The resistance of a conductor is affected by the following factors: • Length of the conductor • Area of cross section of the conductor • Electrical Resistivity of Substances • Effect of Temperature

30. Flow in one direction • Free electrons are necessary for electric current, but for those electrons to move, they need a complete pathway, or circuit, and there must be a force to make them move. The force from a battery sets free electrons moving. • Like charges repel, so the negative electrons are repelled from the negative terminal. Unlike charges attract, so the electrons are also attracted towards the positive terminal. • They flow in one direction only. This is called direct current or DC. Most circuits in motor vehicles use direct current.

32. 1.3 Understand the operation principle of the electronic components

33. Diode • A diode can be thought of as the electronic version of a one-way valve. By restricting the direction of movement of charge carriers, it allows an electric current to flow in one direction, but essentially blocks it in the opposite direction. • A semiconductor diode has a single p-n junction. If it is connected to a current source, with the p region connected to a negative pole, and the n-region to a positive pole, the holes will be attracted towards the negative pole, and the electrons to the positive pole. 

36. Resistor • Resistors are electrical components that resist a current running through them. • Putting a resistor in a circuit causes a drop in voltage across the resistor. So resistors are commonly used to control the voltage that reaches various components. • It is also important to remember that each electrical component also has a resistance of its own. • Most resistors that can carry large currents contain a coil of high-resistance wire wound around a ceramic former to dissipate heat. • Resistance is measured in ohms, represented by a Greek letter, omega, and so resistors are rated in ohms as well, to indicate how strongly they will oppose any current flowing through them. • Resistors also have a wattage rating. This is because resistors work by converting some of the electrical energy passing through them into heat.

37. Resistor ratings

38. Variable resistors • Variable resistors can be adjusted with a control so that the resistance changes, and are called rheostats or potentiometers. An audio volume control knob on an amplifier would be an example of a potentiometer.

39. Thermistors • Thermistors are semiconductor resistors. Their electrical resistance varies according to temperature. This makes them suitable for temperature measurement, and for electronic control operations. • There are two main types of thermistor – NTC (Negative Temperature Coefficient) resistors, and PTC (Positive Temperature Coefficient) resistors.

40. NTC resistors have lower resistance at high temperatures, which means they conduct current more readily when they are hot than when they are cold. NTC resistors are commonly used in temperature sensors in engine management systems. • PTC resistors have higher resistance at high temperature, which means they conduct current less readily when they are hot than when they are cold. This makes them useful as current limiting protective devices in circuits, instead of fuses. As the current increases, the heat generated by the resistor increases, which reduces the amount of current passed.

41. PTC

42. NPC

43. Transistor • Transistors are semiconductor devices used as switches, and to amplify currents. They are a key component in almost any electronic device. • There are two kinds, npn and pnp. The npn transistorhas a p-type semiconductor between two n-type semiconductors. A pnp transistor has an n-type, between two p-types. • Each of the three regions has a terminal. The center region is always called the base. The outer regions are the collector, and the emitter. In the symbol, the emitter is the terminal with the arrow. always pointing to the negative material.

45. In a circuit, npn transistors can act as a switch. If the control switch is open, the depletion layer at one pn-junction is blocking current from flowing through the transistor and driving the load. • With a closed control switch, a small current flows through the emitter-base pn-junction. The base has only a limited number of charge carriers, so extra ones flow across the emitter-collector pn-junction, letting current operate the load. The transistor then operates as a low-resistance conductor. A small current through the base lets larger current flow across the emitter-collector junction. The transistor is then said to be turned on.

46. Transformer • A transformer is a simple electrical machine most commonly used to change voltage levels from one value to another in different parts of electrical circuits. • A transformer can step voltage up or down. A basictransformer has two tightly coiled loops of wire called 'windings' coupled together, a primary winding and a secondary winding. These are usually wound around a laminated soft iron core. When a current is introduced into the primary winding, a voltage is induced in the secondary winding. Varying the relative number of winding turns in the two windings determines the variation between the input and output voltages. • A step up transformer increases the voltage from the primary winding to the secondary winding, while a step down transformer decreases the voltage from the primary winding to the secondary winding.