Resistors

Find the resistors in your kit. There is a picture of them at right. When you apply a voltage to one of these, a current results that is proportional to the voltage but also determined by the resistance of the device. Keeping the voltage constant (3 V, for example), we can get very different currents, as indicated in the table below.

Notice that there are colored bands on the resistors. These are labels that tell the resistance. The kit contains these values:

Color code Value Current
at 3 V
10 Ohm brown-black-black 10 Ohms 0.3 Amp
100 Ohm brown-black-brown 100 Ohms 0.03 Amp
1000 Ohm brown-black-red 1000 Ohms 0.003 Amp
10000 Ohm brown-black-orange 10000 Ohms 0.0003 Amp
This coloring system is frequently used to label electrical components. The first two bands give a numerical value, and then the third band tells how many zeroes to add. The color of the bands represent numbers: black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, purple=7, gray=8, white = 9. Thus a 29,000,000 Ohm resistor would be red, white, and blue.
resistors
Resistors
The gold band at the right describes the precision of the resistor.
The colored bands on the left tell the resistance.
The symbol for a resistor is resistor, because the early resistors were long wires which were folded up to save space. Notice from the table that increasing the resistance decreases the current.

Put a resistor in series with a light bulb, a buzzer, or a light-emitting diode, as you were just doing in the previous activity. comparing resistances If the current that the resistor permits is larger than the current the device needs, the device continues to work, and the resistor doesn't have much effect on it. If the current that the resistor permits is much smaller than the current the device needs, the device doesn't do anything. If the current that the resistor permits is about the same as the current the device needs, it will function but not quite as well (the light bulb is only half as bright, for example). write in your journal Fill in this table indicating what happens with each combination of resistor and device, to determine the current that each device needs.


When we change a circuit so that the current increases, we are also increasing the power that the circuit uses. So which are the high power devices among the ones studied in this activity?



Check the box when you are done: check box 
Next:Resistors and capacitors