Hands-On-Physics

IEU Concepts
CIRCUITS

Current: Current is the flow of electricity, the number of electrons that pass a point in a second. Since the number of electrons is measured in coulombs, current is measured in coulombs/second, or amperes (a), usually called amps. One coulomb has a lot of electrons, about 16,000,000,000,000,000,000.

Voltage: is the amount of energy each electron has. Since it is the energy per electron, it is measured in joules/coulomb, or volts (V). Voltage is often visualized as the "push" behind current.

Its a good idea to keep these definitions firmly in mind. You can make an analogy to a platoon of soldiers completing a 10 mile hike in formation. The electrons would be represented by the soldiers, the current by the number of soldiers that pass a point in one second, and the voltage by the energy each soldier has. In a simple series circuit, where the soldiers have only one path, the current will be the same, because no soldiers are gained or lost on the hike (hopefully!). The voltage will decrease during the hike as the soldiers tire; there will be less energy per soldier. In an electrical circuit this energy is lost at any resistor or other component that uses power.

Circuit Diagram: Important skills to develop in this unit include drawing circuit diagrams and building circuits using diagrams. We have included pictures of completed circuit boards and sketches of circuit boards, but if you are using them without learning the circuit diagrams, you are missing something. The rest of the world uses the diagrams, and you should learn to make using the diagrams as familiar as using the sketches. To help with that, try putting the line numbers of your circuit board on the diagrams. Then everything on that wire of the diagram goes into the same line on the circuit board. This may also help you in debugging our circuit board.

Debug: The last big skill in this unit is to debug circuit boards. This is usually mandatory, time consuming, and can be frustrating. Perhaps if you expect to have to do it it will become less frustrating. Try the following steps:

1. Proofread your circuit board. Check that every component and jumper wire is correct with the diagram. If you numbered your lines as suggested above, this will take less time. Have your partner proofread, too.
   
   
2. Check all your connections. Often some wire lifts up and a connection is broken. Use your needlenose pliers to make sure each wire is down.
   
   
3. Use the multimeter to check for conductivity and voltage loss at various points to see if you can locate the problem area.
   
   
4. Switch components--ONE AT A TIME--with another lab group to see if you have a defective component.
   
   
5. If all else fails, ask your teacher for help.