Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Schmitt trigger wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Power electronics wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Electric charge wikipedia , lookup
Power MOSFET wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Voltage regulator wikipedia , lookup
Current mirror wikipedia , lookup
Nanogenerator wikipedia , lookup
Opto-isolator wikipedia , lookup
Voltage Review • What do like charges do to each other? • What do opposite charges do to each other? • If you want to get like charges closer together, what do you have to do on them? • Consider the picture of the slide. How do the kids get energy to go down the slide? • They do work on themselves climbing the stairs. That work done equals their gain in Gravitational Potential Energy. • W=F∙d To bring like charges together… WORK must be done! How can charges gain energy? • Charges gain energy when work is done on them bringing like charges closer together. • This work done gives the charge more Electric Potential Energy or EPE. What energy can PE turn into? When a charge gains EPE and is then released, the EPE turns into KE. Conservation of energy! The Math: If you take EPE and divide by the amount of charge the object has you get a value called Voltage. Voltage is a measure of the amount of Energy per Charge. How much energy does 1C of charge have as it exits a 6V battery? 1. 2. 3. 4. Voltage Names for Potential Electric Potential Electric Potential Difference (next slide) • 5. Voltage Drop 6. EMF = electro-motive force 7. Electric Pressure, (conceptual name) because Voltage is the pressure that causes flow. Reason: EPE turns into KE when a charge is released (flow). Voltage Electric potential Energy is not voltage, it is energy. Electric Potential Difference • Will water flow from one container to the other in the top right image? • Will water flow in the bottom right image? Why? • For Electricity (electrons) to flow from one source into another we need more than just Voltage (electric pressure), we need a DIFFERENCE in voltage. • Example: If the water pressure in the plumbing of your home is 60psi, why does the water flow out of the faucet when you open it? • Would water flow out of the faucet if the pressure at the opening was also 60psi? • It takes a difference in voltage to produce flow of electrons. Voltage Drop • Potential Difference can also be described as Voltage Drop. • When you go to work, you give some of your energy to your employer and have less energy when you leave work compared to when you arrived. • A similar situation exists as charge (electrons) pass through a device, the energy they possess is given to the device leaving them with no energy as they exit. • Recall V=PE/q, so the PE is transferred and converted into new forms of energy as the electrons pass through the device, dropping the voltage to zero as charge reaches the end (exits the device). • Important to note: charges are NOT consumed or used up in this process, just the energy they carry is transformed! Ohm’s Law : • Recall that Voltage is conceptually the pressure that produces flow of charge. • Flow is electrically called Current (the rate at which electrons flow) and is defined as: • I= q/t, measured in Amperes. 1 Amp = 1 C of charge flowing past a point every 1 second. (1 A = 1 C/s) • Resistance is a measure of how easily charge moves through a conducting material and is measured in ohms (Ω). • http://phet.colorado.edu/en/si mulation/ohms-law Putting them all together… (Ohm’s Law) • We get the following math relationship: • I=V/R • This reveals that: Current is directly related to Voltage and inversely related to Resistance. • So we have 2 equations to solve for voltage and current. What causes Resistance http://phet.colorado.edu/en/simulation/resistance-in-a-wire Resistivity The resistance of a wire depends on its dimensions and the resistivity of its material: • L = Length of resistor (m) • A = cross-sectional Area of resistor (m2) • ρ = Resistivity and depends on the material used. See pg. 721, Table 22.1. (Ω·m) Checking Understanding A battery is connected to a wire, and makes a current in the wire. Which of the following changes would increase the current? (1) Increasing the length of the wire; (2) keeping the wire the same length, but making it thicker; (3) using a battery with a higher-rated voltage; (4) making the wire into a coil, but keeping its dimensions the same; (5) increasing the temperature of the wire. A. B. C. D. E. All of the above 1 and 5 1, 4, and 5 2 and 3 None of the above Answer A battery is connected to a wire, and makes a current in the wire. Which of the following changes would increase the current? (1) Increasing the length of the wire; (2) keeping the wire the same length, but making it thicker; (3) using a battery with a higher-rated voltage; (4) making the wire into a coil, but keeping its dimensions the same; (5) increasing the temperature of the wire. A. B. C. D. E. All of the above 1 and 5 1, 4, and 5 2 and 3 None of the above Electric Current • Recall that metals are good conductors which means that electrons move easily through them. • Here are some visual examples… • Ben Franklin actually said that it was the positive charges that flow. Today, we call this CONVENTIONAL CURRENT. • A schematic diagram is a Schematic drawing of the path charge takes in traveling through different objects. • The short and long parallel lines on the left represent 2 batteries • The zig zag line on the right represents a resistor which is anything that actually uses electrical energy like a hair dryer or light bulb. • The line connecting them represents wire. Diagram Voltmeter and measuring volts • Note that the black wire is plugged into the COM port and the red wire is in the V port. Voltage is measured by touching the test leads to opposite ends of the device you want to measure. • The meter wires are connected PARALLEL to the device being tested. Ammeter and measuring Amps • Note the black wire is still in the COM port but the red wire moves to the A port, specifically the 10A port. • Current is measured by producing ONE path for electricity to flow through all devices all at once. • We say the meter is connected in SERIES with the device being tested. In Series means one right after the other or in line. • Recall power is the rate that energy is being converted or used (HP lab) • P = Energy/time or • Energy = P·t • 1 Joule = 1 watt·1 sec. • P = V· I • 1 watt = 1volt·1amp Electric Power Summary