* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download LAB:Ohm`s Law
Integrating ADC wikipedia , lookup
Negative resistance wikipedia , lookup
Galvanometer wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Opto-isolator wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Schmitt trigger wikipedia , lookup
Surge protector wikipedia , lookup
Power electronics wikipedia , lookup
Operational amplifier wikipedia , lookup
Two-port network wikipedia , lookup
Valve audio amplifier technical specification wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Charlieplexing wikipedia , lookup
Power MOSFET wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Rectiverter wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Network analysis (electrical circuits) wikipedia , lookup
Current mirror wikipedia , lookup
Current source wikipedia , lookup
Name __________________________ Period ______ Date _______________ Lab Partners _____________________ _____________________ _____________________ _____________________ V Ohm’s Law Lab I=V R Purpose: To verify Ohm’s Law by showing that current is directly proportional to voltage and inversely proportional to resistance. Materials: Variable Power supply that can be set between 1.5V and 6.0 volts (no higher than 6 V)or two batteries Three different value 0.5 watt resistors resistors ranging from 33 ohms to 500 ohms Three wire leads Multimeter Procedure: Part I Read and record the values of the three different resistors you chose, including the tolerance (%error) factor for each reading. Set the multimeter to read ohms and measure the resistor value for each of the three resistors you chose, as shown in the diagram below. Using the Multimeter To measure Resistance Part II Set up a simple series circuit with the power supply connected to the first of your resistors Set the voltage to 1.5 volts (or use a single dry cell) and turn the power supply on Set the multimeter to read DC Volts at its lowest reading, then turn on the multimeter Measure and record the voltage across the resistor as demonstrated in class and in the picture below by: o touching the positive probe to the side of the resistor leading to the positive connection at the power source and simultaneously o touching the negative probe to the side of the resistor leading to the negative connection at the power source (see diagram on following page) Using the Multimeter as a Voltmeter Power source Remove the probes from the resistor and turn off the multimeter. Part III To measure and record the current through the resistor: o Disconnect the negative end of the resistor from the power source and attach it instead to the positive probe on the multimeter. o Attach the negative probe of the multimeter to the negative power source outlet. o Turn the multimeter dial to measure the smallest amount of DC current (DC Amps) o Turn on the multimeter and record the current measurement, being careful to note the prefix (milli-, micro-) before the amperage reading. Using the Multimeter to measure Current Part IV Repeat the above steps after setting the voltage to double (3V instead of 1.5V) Repeat the above steps with each of the other two different value resistors. Part V Calculate the current for each different trial using Ohm’s Law and compare your calculated value of current to your measured value for the current using a % difference calculation Questions: 1. Draw a circuit diagram below showing the setup for this experiment by using the appropriate circuit symbols. Be sure to include the power source, the resistor, the ammeter, and the voltmeter in your diagram. Label each device with the appropriate letter. 2. According to your lab results, what relationship exists between the voltage and the current through a particular resistor? 3. According to your lab results, what relationship exists between the resistance and the current at a certain voltage? 4. How accurate was the resistor code on your resistors? What percent error did you find between your highest value resistor code reading and actual resistance you measured for that resistor using the ohmmeter? Was the % error within what was claimed by the gold or silver resistor tolerance bands? 5. Did the lab prove Ohm’s Law to be true? How do you know? Name ________________________ Resistors and Resistor Codes Built into any appliance are devices called resistors designed to encourage the electron current to give off its energy (called a voltage drop). These resistors are manufactured to have a certain value, measured in “ohms” (or “”), and are often made of ceramic. The value of the resistor is indicated along its length by a series of color bands, the first two of which represent two digits from 0 to 9, and the third of which represents the multiplier, or number of zeros to follow the two digits. The color band code and is read from left to right with the resistor’s gold or silver bands on the right. The code is easy to remember… it follows the colors of the rainbow: Color Black Brown Red Orange Yellow Green Blue Violet Gray White Digit (1st two bands) 0 1 2 3 4 5 6 7 8 9 Multiplier (3rd band) 1 10 100 1000 x 104 x 105 x 106 x 107 x 108 x 109 The gold and silver bands at the other end of the resistor give the “tolerances” or error factor. Gold is 5%, silver is 10%, gold and silver would be 15%. Practice reading the resistor codes on the following page, then on real resistors. Have a partner check your readings. For each of the following resistors, the color bands are stated in the order in which they would appear from left to right. State the value for each resistor on the blank to the right of the resistor. For the last few resistor drawings, use real resistors and indicate the colors of the bands and the value of the resistor in the blanks provided. Red, green, blue, silver Orange, yellow, black, gold Blue, gray, white, gold, silver Green, black, brown, gold Brown, red, black, silver, gold Your choice of resistors: Colors: _________________________________ Colors: _________________________________ Colors: _________________________________