| 106 | | * Unplug the bulb from the circuit above |
| 107 | | * Connect the positive wire (alligator jumper wire connected to the positive battery terminal) to one of the motor wires or terminals |
| 108 | | * Connect the multimeter red wire to the other motor wire or terminal |
| 109 | | * The motor spins! |
| 110 | | * observe the amount of current flowing in Amperes on the multimeter display |
| 111 | | |
| 112 | | * What happened: Just as water turning a hydroelectric turbine in a dam converts some of the mechanical turning energy into electrical energy (flowing electrons), the DC motor converts some of the energy from electrons flowing through it into mechanical rotational energy. The DC motor contains coils of wire that allow electricity to flow from one terminal to the other (and cause the motor to spin in the process). The work the motor can do is proportional to the power (voltage * current) of the electrons flowing through the circuit. |
| | 106 | * Materials needed: multimeter with leads, two jumper wires with alligator clips, SLA or 9v battery, DC motor |
| | 107 | * Activity: |
| | 108 | * Set up materials as in the exercise above |
| | 109 | * Unplug the bulb from the circuit |
| | 110 | * Connect the positive wire (alligator jumper wire connected to the positive battery terminal) to one of the motor wires or terminals |
| | 111 | * Connect the multimeter red wire to the other motor wire or terminal |
| | 112 | * The motor spins! |
| | 113 | * observe the amount of current flowing in Amperes on the multimeter display |
| | 114 | * What happened: Just as water turning a hydroelectric turbine in a dam converts some of the mechanical turning energy into electrical energy (flowing electrons), the DC motor converts some of the energy from electrons flowing through it into mechanical rotational energy. The DC motor contains coils of wire that allow electricity to flow from one terminal to the other (and cause the motor to spin in the process). The work the motor can do is proportional to the power (voltage * current) of the electrons flowing through the circuit. |
| 115 | | * Disconnect the positive wire from the motor terminal it is connected to, noting which terminal that is (we'll call it P) |
| 116 | | * Disconnect the multimeter red wire from the other motor terminal (we'll call it N) |
| 117 | | * Reverse the connections so the positive wire connects to terminal N and the multimeter red wire connects to terminal P |
| 118 | | * The motor spins the other direction! |
| 119 | | |
| 120 | | * What happened: The direction the DC motor spins is determined by the direction of the flow of electrons through it. |
| | 117 | * Materials needed: multimeter with leads, two jumper wires with alligator clips, SLA or 9v battery, DC motor |
| | 118 | * Activity: |
| | 119 | * Set up materials as in the exercise above |
| | 120 | * Disconnect the positive wire from the motor terminal it is connected to, noting which terminal that is (we'll call it P) |
| | 121 | * Disconnect the multimeter red wire from the other motor terminal (we'll call it N) |
| | 122 | * Reverse the connections so the positive wire connects to terminal N and the multimeter red wire connects to terminal P |
| | 123 | * The motor spins the other direction! |
| | 124 | * What happened: The direction the DC motor spins is determined by the direction of the flow of electrons through it. |
| 136 | | * Turn your multimeter on and the range selector to Ohms (often shown with the Greek letter Omega) |
| 137 | | * Plug the black wire into the hole labeled COM |
| 138 | | * Plug the red wire into the hole labeled V/mA/Ohms... |
| 139 | | * Touch the black wire to one of the load wires/terminals |
| 140 | | * Touch the red wire to the other load wire/terminal |
| 141 | | * Observe the resistance measurement on the multimeter display |
| | 140 | * Materials Needed: multimeter with leads, low voltage bulb, DC motor |
| | 141 | * Activity: |
| | 142 | * Turn your multimeter on and the range selector to Ohms (often shown with the Greek letter Omega) |
| | 143 | * Plug the black wire into the hole labeled COM |
| | 144 | * Plug the red wire into the hole labeled V/mA/Ohms... |
| | 145 | * Touch the black wire to one of the load wires/terminals |
| | 146 | * Touch the red wire to the other load wire/terminal |
| | 147 | * Observe the resistance measurement on the multimeter display |
| | 148 | * What happened: The multimeter contains a small battery; it measures the current that flows from its internal battery through the load and uses Ohms law to determine the resistance. |
| 143 | | * What happened: The multimeter contains a small battery; it measures the current that flows from its internal battery through the load and uses Ohms law to determine the resistance. |
| | 150 | * Exercise: Measure the resistance of pencil lead (graphite) |
| | 151 | * Materials needed: multimeter with leads, pencil, paper |
| | 152 | * Activity: |
| | 153 | * Use a pencil to draw a thick dark line on a piece of paper. Go over the same line many times until it is thick and has a lot of graphite. |
| | 154 | * Turn your multimeter on and the range selector to Ohms (often shown with the Greek letter Omega) |
| | 155 | * Plug the black wire into the hole labeled COM |
| | 156 | * Plug the red wire into the hole labeled V/mA/Ohms... |
| | 157 | * Touch the black probe to one end of the black line on the paper |
| | 158 | * Touch the red probe to the other end of the black line on the paper |
| | 159 | * Observe the resistance measurement on the multimeter display |
| | 160 | * Slide the probes closer together and observe how the resistance changes |
| | 161 | * What happened: all substances present some resistance to the flow of electrons; graphite presents a moderate level of resistance. The more graphite the electrons must pass through, the higher the resistance. |
| 145 | | * Exercise: Measure the resistance of pencil lead (graphite) |
| 146 | | * Use a pencil to draw a thick dark line on a piece of paper. Go over the same line many times until it is thick and has a lot of graphite. |
| 147 | | * Turn your multimeter on and the range selector to Ohms (often shown with the Greek letter Omega) |
| 148 | | * Plug the black wire into the hole labeled COM |
| 149 | | * Plug the red wire into the hole labeled V/mA/Ohms... |
| 150 | | * Touch the black probe to one end of the black line on the paper |
| 151 | | * Touch the red probe to the other end of the black line on the paper |
| 152 | | * Observe the resistance measurement on the multimeter display |
| 153 | | * Move the probes closer together and observe how the resistance changes |
| 154 | | |
| 155 | | * What happened: all substances present some resistance to the flow of electrons; graphite presents a moderate level of resistance. The more graphite the electrons must pass through, the higher the resistance. |
| 156 | | |
| 157 | | * Exercise: measure the resistance of other things (e.g. your fingers). Try it with your fingers moist and dry and observe the difference. |
| | 163 | * Bonus Exercise: measure the resistance of other things (e.g. your fingers). Try it with your fingers moist and dry and observe the difference. |
