Question 1

Shown here is the schematic symbol for a resistor:



What is the purpose of a resistor? What function does it perform? Also, draw an illustration of what a real resistor looks like.

 

Question 2

Resistors are sometimes represented in electrical and electronic schematic diagrams by a symbol other than this:



Draw this other symbol next to the one shown above.

 

Question 3

A primitive resistor may be formed by sketching a thick line on a piece of paper, using a pencil (not an ink pen!):



How may the end-to-end electrical resistance of this pencil mark be increased? How may it be decreased? Explain your answers.

 

Question 4

When a resistor conducts electric current, its temperature increases. Explain how this phenomenon is significant to the application of resistors in electric circuits. In other words, why would we care about a resistor’s temperature increasing?

Also, what does this indicate about the technical ratings of resistors? Aside from having a specific resistance rating (i.e. a certain number of ohms), what other rating is important for proper selection of resistors in electric circuits?

 

Question 5

Many resistors have their electrical resistance shown by a set of color codes, or “bands,” imprinted around their circumference. A standard color code associates each color with a specific decimal digit (0 through 9). Associate each of the following digits with its respective color:

0
=
1
=
2
=
3
=
4
=
5
=
6
=
7
=
8
=
9
=

 

Question 6

Observe the following “4-band” resistors, their color codes, and corresponding resistance values (note that the last color band is omitted, since it deals with precision and not nominal value):



What patterns do you notice between the color codes (given as three-letter abbreviations, so as to avoid interpretational errors resulting from variations in print quality), the resistance values, and the physical sizes of the resistors?

 

Question 7

What does the last color band represent on a color-coded resistor?

 

Question 8

Determine the nominal resistance values of these resistors, given their band colors, and also express the allowable tolerance in ohms.

For example, a 25 kΩ resistor with a 10% tolerance rating would have an allowable tolerance of +/- 2.5 kΩ.

Red, Org, Blu, Gld =
Brn, Blk, Grn, Sil =
Blu, Blk, Brn, Gld =
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 =

 

Question 9

Observe the following “5-band” precision resistors, their color codes, and corresponding resistance values (note that the last color band is omitted, since it deals with precision and not nominal value):



What patterns do you notice between the color codes (given as three-letter abbreviations, so as to avoid interpretational errors resulting from variations in print quality) and the resistance values of each resistor? Why do precision resistors use a “5-band” color code instead of a “4-band” color code?

 

Question 10

Determine whether or not the following resistors measure within the resistance range specified by their color codes:

(Org, Org, Red, Blk, Blu) Measured resistance = 332.5 Ω
(Brn, Blk, Blk, Gld, Red) Measured resistance = 9.7 Ω
(Blu, Vio, Brn, Red, Grn) Measured resistance = 67.43 kΩ
(Red, Wht, Grn, Yel, Vio) Measured resistance = 2.949 MΩ
(Yel, Vio, Org, Gld) Measured resistance = 44.68 kΩ
(Gry, Red, Brn, Sil) Measured resistance = 905 Ω
(Grn, Blu, Gld) Measured resistance = 6.73 Ω
(Vio, Brn, Red, Gld, Brn) Measured resistance = 70.82 Ω
(Wht, Org, Blu, Brn, Grn) Measured resistance = 9.38 kΩ
(Red, Blk, Wht, Grn, Vio) Measured resistance = 20.86 MΩ

Assume that all five-band resistors listed here use the precision color code as opposed to the military 5-band code where the fifth band indicates resistor reliability.

 

Question 11

Find one or two real resistors and bring them with you to class for discussion. Identify as much information as you can about your resistors prior to discussion:

Resistance (ideal)
Resistance (actual)
Power rating
Type (carbon composition, metal film, wire-wound, etc.)

 


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