Introduction to Electrical Circuits - Lecture Slides | ESE 112, Study notes of Electrical and Electronics Engineering

Download Introduction to Electrical Circuits - Lecture Slides | ESE 112 and more Study notes Electrical and Electronics Engineering in PDF only on Docsity! 1 ESE112 Introduction to Electrical Circuits Application - Robotics Sensors to get information A device that measures a physical quantity and converts it into a signal (electrical) E g Thermistor to measure temperature Thermistor . . • Type of resistor whose resistance varies with temperature Actuators used in navigation Electrical energy is converted in mechanical energy to drive motors • Usually interaction of magnetic fields and current carrying ESE112 2 - conductors • Video of simple motor Simple Electric Motor Electric Charge Fundamental to all electrical phenomena Is a property of atomic particles of which matter exists Protons(+ve), Electrons (-ve) Measured in Coulombs(C) 1 C = 6 2 x 1018 charged particles ESE112 3 . Voltage & Current Charges become mobile if there is force to move them Voltage (V) is the energy required to move a unit charge through an element • Potential difference between two points • Measured in Volts (V) i.e. 1 Joule/1 Coulomb Motion of charges creates Electric Current Current is the rate of flow of charge ESE112 4 • Measured in Amperes (A) i.e. 1Coulumb/1sec • Current flows from high-potential to low potential • The direction of the current is taken to be as the movement of positive charges i.e. opposite to flow of negative charges 2 Battery - electromotive force 2 different metals in a chemical solution One metal +ve charge and other –ve charged If a wire (conducting material e g copper) is . . attached from one end of the battery to the other then Electrons flow through the wire to balance the electrical charge If a load such as a lightbulb is placed ESE112 5 along the wire, the electricity can do work as it flows through the wire Battery (contd..) House-hold solution Lemon Battery Cu (penny) - +ve Zinc (galvanized nail) –ve Commercial AA – Zinc & carbon Alkaline – Zinc & Manganese Oxide Car battery - Lead-acid ESE112 6 AC vs. DC current Alternating Current (AC) Current that varies (sinusoidal) with time • Wall socket provide AC that alternates 60 times per second Easy to change the voltage, using a device called a transformer Direct Current (DC) Batteries, solar or fuel cells produce current that remains constant with time Current always flows in the same direction between two (positive and negative) terminals ESE112 7 Resistance (R) Is the opposition to the flow of charge Depends on Di tl ti l trec y propor ona o length of element (l) Inversely proportional to cross-sectional area (A) Inversely proportional to conductivity of the element Measured in Ohms (Ω) ESE112 8 Passive element Element which is not a source of energy 5 Diode Allows electricity to flow in only one direction The arrow of the circuit symbol shows the direction in which the current can flow Modern diodes are realized from semi- conductors Semiconductor Semiconductor material are in between conductors (like metals) and insulators (like glass) In pure form it is non conducting , - E.g. silicon crystal - has 4 electrons in its outer orbital, which form perfect covalent bonds with four neighboring atoms, leaving no electrons to conduct electric current You can change the behavior of silicon and turn it into a conductor by doping it. In doping, you mix a small amount of an impurity into the silicon crystal N-Type & P-Type Semiconductors N-Type Semiconductor - Abundance of electrons - N for negative charge - E.g. Phosphorous as dopant P-Type Semiconductor Ab d f iti h- un ance o pos ve c arge - P for positive charge - E.g. Boron as dopant Semiconductor Diode At the junction, free electrons Electrons and holes start i d th d l tifrom the N-type material fill holes from the P-type material This creates an insulating layer in the middle of the diode called the depletion zone mov ng an e ep e on zone disappears 6 LED (Light Emitting Diode) Photons (energy in form of light) are released as a result of moving electrons In an atom, electrons move in orbitals around the nucleus Electrons in different orbitals have different amounts of energy Electrons with greater energy move in orbitals farther away from the nucleus. For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level Conversely an electron releases energy when it drops, from a higher orbital to a lower one. This energy is released in the form of a photon. Band Gap ESE112 22 Source: http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Conduction_band LED Anode – Long end Cathode – short end T i ll t LED b typ ca y opera e s e ween 5-20 mA Never connect an LED directly to a battery or power supply! It will be destroyed almost instantly because too much current will pass through and burn it out