1. Lets look at the resistivity of elements on the periodic table:
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2. Types of Resistors
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3. Carbon resistors
Resistors are used to step down the voltage flowing through a circuit.
The center of the resistor is made from a material that is only a partial conductor of electricity, like carbon.
When the voltage reaches the part of the resistor that is a poor conductor, the voltage is reduced or stepped down.
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5. Let’s Observe Resistors
Make at least 4 observations of the resistors at your desk.
Record your observations on the post-it notes provided.
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6. Resistors: Reading the Resistor Color Code

7. Observing Resistors
There is a gap between the bands that indicate resistance value and the band that represents tolerance.
Values, Multipliers and Tolerances
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8. Tolerance of resistors (fourth band of color code)
Tolerance is the precision of the resistor and it is given as a percentage.
For example a 390 resistor with a tolerance of ±10% will have a value within 10% of 390, between = 351 and = 429 (39 is 10% of 390).
Find the tolerance of a 10M resistor. Calculate the range of the possible values of the resistor.
Tolerance may be ignored for almost all circuits because precise resistor values are rarely required.
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10. First Example:
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11. Let’s Practice with these…
Determine the nominal resistance values of these resistors, given their band colors, and also express the allowable tolerance in ohms. Red, Org, Blu, Gld =
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12. Brn, Blk, Grn, Sil =
Blu, Blk, Brn, Gld =
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13. For more practice, try these and check them with the applet on the next slide.
Yel, Vio, Red, Sil =
Grn, Brn, Yel =
Wht, Blu, Blk, Sil =
Gry, Grn, Org, Gld =
Org, Org, Gld =
Vio, Red, Sil, Gld =
Brn, Red, Blk, Sil =
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14. Use this applet to check your answers:
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15. Resistors and Color Code Tutorial: http://www. youtube. com/watch
Resistors and Color Code Tutorial: Short Animation describing resistance: Using a simple circuit and graphite from your pencil as a variable resistor
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