Function Of Variable Resistor; Function Of Photo Resistor - Elenco Electronics Snap Circuits Instruction Manual

Project #325
Project #326
-15-
Function of Variable
Resistor
OBJECTIVE: To understand the function of the variable resistor.
A variable resistor is a normal resistor with an additional arm contact.
The arm moves along the resistive material and taps off the desired
resistance.
The knob on the variable resistor moves the arm contact and sets the
resistance between the left and center pins. The remaining resistance
of the part is between the center and right pins. For example, when the
dial is turned fully to the left, there is minimal resistance between the left
and center pins (usually 0Ω) and maximum resistance between the
center and right pins. The resistance between the left and right pins will
always be the total resistance, (50kΩ for your part).
Adjust the variable resistor (RV) for maximum resistance by setting the
knob to the top. The meter (M2) only deflects ¼ of the way. As you move
the knob down, decreasing the resistance, the meter deflects more.
Function of Photo
Resistor
OBJECTIVE: To understand the function of the photo resistor.
Build the circuit shown. The photo resistor (RP) is a light-sensitive
resistor. Its value changes from nearly infinite in total darkness to
about 1000Ω when a bright light shines on it.
The meter reading changes as the resistance changes in the circuit.
When the lights are on, the meter (M2) points to the right of the 5 on
the scale. When the lights are OFF, the pointer will be to the left of the
5. This means that the resistance of the photo resistor is changing
according to the amount of light in the room.