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| | + | = References = |
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| − | == Description ==
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| − | In this lab you will use a Digital MultiMeter (DMM) to take measurements in a simple circuit.
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| − |
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| − | * First read the required reading material indicated in the schedule for the Intro into Electronics: [[PracticalTheExpandedToolbox#Schedule]]
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| − | * Read the SparkFun tutorial on [https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter using the a Digital Multi Meter]
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| − | * Keep track of you measurements and note these down on your WiKi.
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| − |
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| − | If you don't know how to use the WiKi yet note them down elsewhere so you can note them on the WiKi after the WiKi introduction.
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| − | For the current and voltage measurements you need to create a simple circuit on for example a breadboard consisting of a battery, led and a resistor:
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| − | [[File:led_breadboard.png|200px|thumb|center|Example LED circuit for voltage and current measurements]]
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| − | Remember an LED has polarity. If you hook it up the wrong way it won't light up. The long leg is the anode or +, the short leg is the cathode or -. See https://learn.sparkfun.com/tutorials/light-emitting-diodes-leds#how-to-use-them for more details on LEDs and how to use them.
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| − |
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| − | === Measuring Voltage ===
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| − | What you need (ask at the Interaction Station):
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| − | * Multimeter
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| − | * 9 Volt battery ''(5V in the tutorial)''
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| − | * 9 Volt battery clip for in a breadboard
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| − | * 470 Ohm resistor ''(1K Ohm in the tutorial)''
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| − | * LED
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| − | * breadboard
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| − |
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| − | * Carry out the SparkFun tutorial section about measuring voltage: https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter#measuring-voltage .
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| − |
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| − | '''Note 1:''' instead of the 5V breakout board the tutorial uses you are using a 9V battery. This means your measured values will differ from the results in the tutorial. Your resistor value and LED forward voltage will differ as well.'''
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| − | <br/>
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| − | <br/>
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| − |
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| − | === Measuring resistance ===
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| − | What you need (ask at the Interaction Station):
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| − | * Multimeter
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| − | * 3 random resistors
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| − | * 3 resistors of the same value
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| − | * breadboard
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| − |
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| − | Resistors come in a wide variety of values, tolerances, wattage and packages. The most common (hobby)resistor is the 1/4 Watt resistor with a tolerance of 5% (meaning the real value of the resistor can be 5% lower or higher than the indicated value). These resistors are usually beige in colour. At the Interaction Station you will probably get resistors that are light blue. These are still 1/4 Watt resistors but have a tolerance of 1%.
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| − |
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| − | Resistors come in specific values determined by their tolerance range. The range for the 5% tolerance is called the E24 range. The E96 range is for the higher precision 1% tolerance range. For an overview of corresponding values and other ranges see for example: http://logwell.com/tech/components/resistor_values.html
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| − |
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| − | The value of a resistor is encoded on the resistor with [https://learn.sparkfun.com/tutorials/resistors#decoding-resistor-markings color bands]. You can use a resistor color code calculator like: http://www.allaboutcircuits.com/tools/resistor-color-code-calculator/ Resistors of the E24 range (5% tolerance) have a 4 band marking. The blue resistors of the E96 range have a 5 band marking. Be sure to select the right one (4 or 5 strip in the calculator).
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| − |
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| − | * First try to figure out the values you have been given using the colored bands on the resistors.
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| − | * Next carry out the SparkFun tutorial section about measuring resistance: https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter#measuring-resistance
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| − | * Are your measurements within the specified tolerance (5% for the beige resistors, 1% for the blue resistors)?
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| − | <br/>
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| − | Suggested reading for the following experiments: [https://learn.sparkfun.com/tutorials/resistors#series-and-parallel-resistors Resistors in Series and Parallel]
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| − | ==== Series resistance ====
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| − | * Add three resistors in series
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| − | * Calculate the total resistance
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| − | * Measure the total resistance, does it agree with the calculated resistance?
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| − |
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| − | ==== Parallel resistance ====
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| − | * Add two equal resistors in parallel
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| − | * Calculate the total resistance
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| − | * Measure the total resistance, does it agree with the calculated resistance?
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| − | * What can you tell about the total resistance?
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| − | * Repeat with the three equal resistors.
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| − |
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| − | * Add the three random resistors in parallel and calculate or measure the total resistance
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| − | * What can you tell about the total resistance in relation to the resistances of the individual resistors? (hint: is the total resistor larger or smaller than any of the individual resistances).
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| − |
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| − | ==== Extra (Optional) ====
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| − | If you know that the resistance of a conductor can be expressed by R = ρ * (l / A) where ρ is called the [https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity#Resistivity_and_conductivity_of_various_materials electrical resistivity] and is constant for the specific material of the conductor, l is its length and A is the cross-sectional area. Can you explain the results of your parallel and series measurements?
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| − | <br/>
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| − | <br/>
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| − | === Measuring Current ===
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| − | What you need (ask at the Interaction Station):
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| − | * Multimeter
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| − | * 9 Volt battery ''(5V in the tutorial)''
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| − | * 9 Volt battery clip for in a breadboard
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| − | * 470 Ohm resistor ''(1K Ohm in the tutorial)''
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| − | * LED
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| − | * breadboard
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| − |
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| − | * Carry out the SparkFun tutorial section about measuring current: https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter#measuring-current .
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| − | <br/>
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| − | <br/>
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| − | === Measuring voltage and current in a series circuit ===
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| − | What you need (ask at the Interaction Station):
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| − | * Multimeter
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| − | * 9 Volt battery ''(5V in the tutorial)''
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| − | * 9 Volt battery clip for in a breadboard
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| − | * 3 resistors random resistors
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| − | * breadboard
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| − |
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| − |
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| − | * Add three resistors in series and connect to the battery
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| − | * Measure the battery voltage
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| − | * Measure the voltage across each resistor
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| − | * Measure the voltage across each pair of two resistors
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| − | * What can you tell about the voltages measured above in relation to the total battery voltage?
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| − | <br/>
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| − | * Using Ohms law for current (remember: ''I = V / R'') calculate the current through the individual resistors. ''Hint: Remember you should not use the total battery voltage here but the voltage dropped across the resistor and the resistance value of this resistor.''
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| − | * Using Ohms law for current calculate the current through the total resistance. ''Hint: first compute the single total resistance of the 3 resistances in series and use the measured battery voltage.
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| − | * Measure the current through the circuit. Does it agree with your calculations?
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| − | <br/>
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| − | <br/>
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| − | === Measuring voltage and current in a parallel circuit ===
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| − | What you need (ask at the Interaction Station):
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| − | * Multimeter
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| − | * 9 Volt battery ''(5V in the tutorial)''
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| − | * 9 Volt battery clip for in a breadboard
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| − | * 3 resistors random resistors
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| − | * breadboard
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| − |
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| − |
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| − | * Add three resistors in parallel and connect to the battery
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| − | * Measure the battery voltage
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| − | * Measure the voltage across each resistor
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| − | * What can you tell about the voltages measured above?
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| − | <br/>
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| − | * Using Ohms law for current (remember: ''I = V / R'') calculate the current through the individual resistors.
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| − | * Using Ohms law for current calculate the current through the total resistance. ''Hint: first compute the single total resistance of the 3 resistances in parallel (1/Rt = 1/R1 + 1/R2 + 1/R3) and use the measured battery voltage.
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| − | * Measure the current through the circuit. Does it agree with your calculations?
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| − | * What can you tell about the currents through each resistor measured above in relation to the total current in the circuit?
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