| 34 | | * Materials needed: rectangular 9v battery, tongue, courage |
| 35 | | * Activity: Taste (with your tongue) the terminals of a 9v battery to see how 9v feels (this is not dangerous, but will catch your attention) |
| | 34 | * Materials needed: [https://cdn-shop.adafruit.com/970x728/1321-00.jpg rectangular 9v battery], tongue, courage |
| | 35 | * Activity: Taste (with your tongue) the terminals of a 9v battery to see how 9v feels (this is not dangerous, it just tingles) |
| | 36 | * What happened: your wet tongue is a fairly good conductor of electricity and formed the conductive element of a circuit allowing electrons to flow from one terminal of the battery to the other. |
| 44 | | * Exercise: Use a multimeter to measure the voltage of a battery: |
| 45 | | * Turn the multimeter on and move the range selector knob to DC Volts (often shown as DCV or a dashed line over a solid line). If you are not using an auto-ranging meter, choose the voltage range that includes the battery you will measure (e.g. the 20V range if you are going to measure a 12V battery) |
| 46 | | * Plug the black probe wire into the hole labeled COM |
| 47 | | * Plug the red probe wire into the hole labeled V/mA/... |
| 48 | | * Touch the other end of the black wire to the negative (-) terminal of the battery |
| 49 | | * Touch the other end of the red wire to the positive (+) terminal of the battery |
| 50 | | * The multimeter will display the battery voltage |
| 51 | | |
| 52 | | * What happened: the electrical pressure, (the difference in positive vs. negative charge) between the two terminals is measured by the multimeter and displayed. Virtually no energy is consumed from the battery in making this measurement. |
| 53 | | |
| 54 | | * Exercise: Measure the voltage of several different types and sizes of batteries |
| 55 | | * Measure a 9v battery, AA battery, robot SLA battery |
| | 45 | * Exercise: Use a multimeter to measure the voltage of a battery: |
| | 46 | * Materials needed: multimeter with leads, battery (AA, 9v, any battery will do) |
| | 47 | * Activity: |
| | 48 | * Turn the multimeter on and move the range selector knob to DC Volts (often shown as DCV or a dashed line over a solid line). If you are not using an auto-ranging meter, choose the voltage range that includes the battery you will measure (e.g. the 20V range if you are going to measure a 12V battery) |
| | 49 | * Plug the black probe wire into the hole labeled COM |
| | 50 | * Plug the red probe wire into the hole labeled V/mA/... |
| | 51 | * Touch the other end of the black wire to the negative (-) terminal of the battery |
| | 52 | * Touch the other end of the red wire to the positive (+) terminal of the battery |
| | 53 | * The multimeter will display the battery voltage |
| | 54 | * What happened: the electrical pressure, (the difference in positive vs. negative charge) between the two terminals is measured by the multimeter and displayed. Virtually no energy is consumed from the battery in making this measurement. |
| | 55 | * Bonus Exercise: Measure the voltage of several different types and sizes of batteries: [https://cdn-shop.adafruit.com/970x728/1321-00.jpg 9v], [https://cdn-shop.adafruit.com/970x728/3349-00.jpg AA], [https://cdn.shopify.com/s/files/1/1490/5112/products/02302538_00_1024x1024.jpg SLA] |
| 69 | | When electrons are allowed to flow between the positive and negative battery terminals, we have a *circuit* and the battery's chemical reaction proceeds (until the chemical reaction is complete). The number of electrons flowing between the terminals is called "Current" and is measured in [https://en.wikipedia.org/wiki/Ampere Amperes] aka Amps (named after [https://en.wikipedia.org/wiki/Andr%C3%A9-Marie_Amp%C3%A8re André-Marie Ampère]. The number of electrons flowing depends on how many electrons the battery can supply (how fast the chemical reaction can proceed) and the nature of the path carrying the electrons from one terminal to the other. You can measure current using your multimeter in the next section. |
| | 69 | When electrons are allowed to flow between the positive and negative battery terminals, we have a *circuit* and the battery's chemical reaction proceeds (until the chemical reaction is complete). The number of electrons flowing between the terminals is called "Current" and is measured in [https://en.wikipedia.org/wiki/Ampere Amperes] aka Amps (named after [https://en.wikipedia.org/wiki/Andr%C3%A9-Marie_Amp%C3%A8re André-Marie Ampère]. The number of electrons flowing depends on how many electrons the battery can supply (how fast the chemical reaction can proceed) and the nature of the path carrying the electrons from one terminal to the other. |
| | 70 | The electron flow generated by a chemical battery or a solar cell is always from one terminal to the other; this is called ''Direct Current'' or ''DC''. Electricity can be generated in other ways such as turning an electromagnetic generator (alternator in your car, steam turbines in a power plant, etc.); when generated in this way, electrons are alternately pushed then pulled by the same terminal of the generator which is called ''Alternating Current'' or ''AC''. The electricity from a wall outlet is alternately pulled/pushed 60-times per second. |
| | 71 | |
| | 72 | You can can measure DC and AC current flow using your multimeter in the next section. |
| 75 | | * Connect one end of an alligator clip jumper wire to the negative (-) terminal of the battery; this will be called the negative wire. |
| 76 | | * WITHOUT letting it touch the negative wire, connect one end of another alligator clip jumper wire to the positive (+) terminal of the battery; this will be called the positive wire. |
| 77 | | * Connect the other end of the negative wire to one terminal on a bulb |
| 78 | | * Connect the other end of the positive wire to the other terminal on a bulb |
| 79 | | * Let there be light! |
| 80 | | |
| 81 | | * What happened: the two jumper wires and the wire filament in the bulb provide a path for the electrons to flow from the negative battery terminal to the positive battery terminal, creating a complete circuit. As the electrons flow through the circuit, the resistance they encounter as they push their way through the bulb's filament cause it to get hot, glow, and emit light. |
| | 78 | * Materials Needed: battery, two jumper wires with alligator clip ends, low-voltage light bulb |
| | 79 | * Activity: |
| | 80 | * Connect one end of an alligator clip jumper wire to the negative (-) terminal of the battery; this will be called the negative wire. |
| | 81 | * WITHOUT letting it touch the negative wire, connect one end of another alligator clip jumper wire to the positive (+) terminal of the battery; this will be called the positive wire. |
| | 82 | * Connect the other end of the negative wire to one terminal or wire of the bulb |
| | 83 | * Connect the other end of the positive wire to the other terminal or wire of the bulb |
| | 84 | * Let there be light! |
| | 85 | * What happened: the two jumper wires and the filament in the bulb provide a path (circuit) for the electrons to flow from the negative battery terminal to the positive battery terminal. As the electrons flow through the circuit, the resistance they encounter as they push their way through the bulb's filament cause it to get hot, glow, and emit light. |
| 86 | | * Exercise: use a multimeter to measure the current flowing through the light bulb circuit |
| 87 | | * Turn the multimeter on and move the range selector to DC Amps (usually marked with an A) |
| 88 | | * Plug the black wire into the hole labeled COM |
| 89 | | * Plug the red wire into the hole labeled 10A |
| | 90 | * Exercise: use a multimeter to measure the current flowing through alight bulb circuit |
| | 91 | * Materials Needed: multimeter with leads, battery, two jumper wires with alligator clip ends, low-voltage light bulb |
| | 92 | * Activity: |
| | 93 | * Turn the multimeter on and move the range selector to DC Amps (usually marked with an A) |
| | 94 | * Plug the black wire into the hole labeled COM |
| | 95 | * Plug the red wire into the hole labeled 10A |
| 91 | | * disconnect the negative alligator wire from the bulb and connect it to the black multimeter wire |
| 92 | | * connect the red multimeter wire to the bulb terminal that had previously been connected to the black wire |
| 93 | | * observe the amount of current flowing in Amperes on the multimeter display |
| 94 | | |
| 95 | | * What happened: The multimeter is now part of the circuit; the electrons flowing through the multimeter and the bulb as they proceed from the negative battery terminal to the positive terminal. |
| 96 | | The multimeter measures the number of electrons flowing through it. |
| | 97 | * disconnect the negative alligator wire from the bulb and connect it to the black multimeter wire |
| | 98 | * connect the red multimeter wire to the bulb terminal that had previously been connected to the black wire |
| | 99 | * observe the amount of current flowing in Amperes on the multimeter display |
| | 100 | * What happened: The multimeter is now part of the circuit; the electrons flowing through the multimeter and the bulb as they proceed from the negative battery terminal to the positive terminal. The multimeter measures the rate of electrons flowing through it. |
