Use a torch and/or other light source to control a device (switch device on/off).

The torch is powered by three AAA batteries contained in a black plastic housing that slides into the body of the torch. The negative ends of the batteries should be inserted to connect with the springs in the battery housing. There is a rubber coated, press-button on/off switch on the removable screw-cap on the base of the battery. The torch circuit is normally OPEN. Pressing the button creates a CLOSED circuit and the torch is turned ON.

When the bottom cap (on/off push-button) is removed, a CLOSED circuit can be created by connecting the metal body of the torch to the base of the metal tracks on the battery holder (see images below).

1. Create a series circuit using the test kit and alligator clips to turn the LED ON/OFF as per 'Circuit' image below:
   1. Test procedures:
      1. With base of torch removed, attach an alligator clip to the open bottom of main body of the torch
      2. Press the other alligator clip against the metal strip on the base of the battery holder inside the torch
      3. Make sure LED turns ON when circuit is 'closed' and OFF when circuit is 'open'.
      4. Remove the alligator clips and CAREFULLY screw the bottom back on to the torch. The bottom will be 'springy' so you will need to be patient and careful.
      5. Make sure that the torch switches ON/OFF using the press-button switch on the base of the torch.
2. Your teacher will allocate and connect a 'night light' to be used by each team.
   1. Create a shield for your night-light:
      1. The 'night light' needs to be shielded from light but also open so that light can shine onto it from one side using a torch.
      2. Create a shield for the night-light by rolling up black paper to make a light tube.
      3. Make sure that one side of the tube is open so that if you look down it, you can see the light on the top of the night-light pointing toward you (see photo)
      4. When the tube is set up and properly shielded, the night light should be ON and it should glow like a lamp. If the light does not glow, then make sure the power is turned on and reduce the amount of light falling on the night light unit (place the unit under a table or some similar shaded location).
3. Turn on your LED test light/torch and point it into the open end of the black tube of the night light that was allocated to you by your teacher.
4. The night light should turn OFF when you shine your LED test light onto it.
   1. It should turns ON if/when you turn you test light/torch OFF, or when you point your test light away from the night light.
   2. Find out how close your test light/torch needs to be to the night light to get the night-light to turn off:
      1. What is the maximum distance between the LED and the night light to get the light to work reliably?
      2. Measure and enter the distance into your results table.
      3. Shine your LED onto the night light from different angles - do some some angles/positions work better than others?
      4. Why does the night light turn off when light shines on it?
      5. Do you know of any practical applications that use this principle?
5. Enter results into results section and your observations into the comments section

Circuit: Remove base: Make connection from case to metal track on battery holder

Alternative lesson plan from ABC is here: lesson_plan11.pdf