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Electricity and Circuits Career Portals in STEM 1 A day in the life of an electrical engineer • http://www.youtube.com/watch?v=I1hX G_H97Sc&feature=player_detailpage 2 What Do Engineers Do? • Study the forces of nature • Apply them to do useful things • Example: Water Wheel – What are the forces? – How is it useful? 3 Water Wheels + 4 = • Water-wheels are Mechanical Engineering • Today, we’ll look at Electrical Engineering What do you need to make a Water Wheel Work? • Water – Makes everything work • River – Source of flowing water • Pipes – To direct the water where you want it to go and regulate the flow • Wheel – To convert the force of the flowing water into force to grind the wheat 5 What’s a similar Electrical Engineering Problem? • Turn on a light – Water → – River → – Pipes → – Wheel → 6 Electricity Battery Resistors, Wires Light Bulb What do you need to make a Light Bulb Work? • Electricity – Makes everything work • Battery – Source of flowing Electricity • Resistors, Wires – To direct the electricity where you want it to go and regulate the flow • Light Bulb – To convert the force of the flowing electricity into light 7 Terminology • Electric Potential – like the height of the water – Symbol (V) – Units (Volts - V) • Current – like the number of gallons of water that flow every second – Symbol (I) – Units (Amperes – A) • Power – like the amount of wheat that can be ground each second, or brightness of light 8 – Symbol (P) – Units (Watts – W) – NOTE: P=I*V Battery • Source of constant potential (9 V) • + lead (red wire) – outflow from high potential • - lead (black wire) – inflow to low potential 9 Light-Emitting Diode (LED) • Emits light when current flows through it • Current can only flow in one direction, from + to (like a water wheel that won’t go in reverse) – Long lead (+) – Short lead (-) 10 Resistor • New term: – Resistance – how easy is it for current to flow – Symbol (R) – Unit (Ohm – Ω) – NOTE: V=I*R • New circuit element – – – – 11 Resistor Regulates the flow of current Like a pipe for electric current to flow Resistance ~ 1/cross-section-area • A wire is like a resistor with a very low Resistance Breadboard Seperate Node Connected • Breadboards are used to connect things quickly One Node Not Connected • You can proto-type circuits quickly 12 Capacitor • Like a glass that holds water – Top of glass (+) long lead (no stripe), should always be at high potential – Bottom of glass (-) short lead (with stripe), should always be at low potential • The more electricity flows in, the higher the voltage (water level) • A large capacitor is like a wide glass 13 – Needs more water (electricity) to get to the same height (voltage) Digital Circuits • Analog Circuits – What we’ve seen up to now – can have any voltage (in our case, anything between 0V and 9V) – Useful for interfacing to the “real world” • Digital Circuits – can have only two voltages: high & low (in our case, only 0V and 5V) – Useful for processing information reliably 14 Electrical Engineering Background and Overview • Electrical engineering (sometimes referred to as electrical and electronic engineering) is a discipline that deals with the study and/or application of electricity, electronics and electromagnetism. • The field first became an identifiable occupation in the late nineteenth century with the commercialization of the electric telegraph and electrical power supply. • The field now covers a range of sub-studies 15 16 17