Teaching Notes

Encourage the students to follow the sequence of steps in the Student Book rather than trying to build the circuit all at once. By first lighting the LED, they can identify the positive and negative LED leads and connect them to the battery and resistor properly. Incidentally, the resistor can equally well be connected between the positive side of the battery and the positive LED lead. Suggest that the students double-check their circuits before connecting the battery. For Step 6, you can explain to students that plugging in the earphone jack automatically shuts off the radio speaker. If a student wants to try a personal stereo as a sound source, that is certainly OK, but the circuit will not work.

If there is no sound from the speaker with the whole circuit complete, push the LED up against the solar cell, and with the solar cell connected to the amplifier/speaker, here are things to try:

— remove the earphone plug from the radio to make sure that the radio is tuned to a station and that the volume is substantial

— make sure the LED is lit (it should be bright)— be sure the LED is squarely facing the solar cell and touching it

— check all alligator clip connections

If you have only a stereo amplifier and speaker for the whole class, make a station for groups to use when their circuits are complete. You may want to have other students work on Activity 7 or 8 during this time.

Once students complete the activity outlined in the For You To Do section on page 283, they can do a side excursion on Transistors available on the CPU Simulation Activities CD. Directions to the students, teacher notes and designed simulations are available on that CD.