Use a colon (:) to introduce a list or series of items.
Active and passive voices
agreement between indefinite pronouns and their antecedents
agreement involving prepositional phrases
Commas Part Five
Commas Part Four
Commas Part One
Commas Part Three
Commas Part Two
complete and simple predicates
complete and simple subjects
compound complex sentences
compound prepositions and the preposition adverb question
compound subject and compound predicate
compound subjects part one
Confusing usage words part eight
Confusing usage words part five
Confusing usage words part four
Confusing usage words part one
Confusing usage words part seven
Confusing usage words part six
Confusing usage words part three
Confusing usage words part three 2
Confusing usage words part two
First Capitalization List
Indefinite pronouns and the possessive case
Irregular Comparison of Adjectives and Adverbs
irregular verbs part one
irregular verbs part two
Misplaced and dangling modifiers
More Apostrophe Situations
More subject verb agreement situations
Parentheses Ellipsis Marks and Dashes
Periods Question Marks and Exclamation Marks
pronouns and their antecedents
Quotation Marks Part One
Quotation Marks Part Two
reflexive demonstrative and interrogative pronouns
Regular Comparison of Adjectives and Adverbs
regular verb tenses
Second Capitalization List
sentences fragments and run on sentences
singular and plural nouns and pronouns
Sound a like words Part Four
Sound a like words Part Three
Sound a like words Part Two
Sound alike words part one
subject and verb agreement
subject complements predicate nominatives and predicate adjectives
subject verb agreement situations
the adjective clause
the adjective phrase
the adverb clause
the adverb phrase
The coordinating conjunction
the correlative conjunction
the direct object
the gerund and gerund phrase
the indirect object
the infinitive and infinitive phrase
The nominative case
the noun adjective pronoun question
the noun clause
the object of the preposition
the participle and participial phrase
The possessive case
The possessive case 2
The possessive case and pronouns
the prepositional phrase
the subordinating conjunction
The verb be
the verb phrase
Transitive and intransitive verbs
types of nouns
types of sentences by purpose
Using Capital Letters
what good writers do
You should have the following books and supplies with you on the
first day of class: Roget’s Thesaurus, two pencils, a dictionary, and
These are the eight parts of speech: noun, pronoun, adjective, verb,
adverb, preposition, conjunction, and interjection.
Note: A colon should not follow directly after a verb or a preposition.
The following two sentences include incorrect uses of the colon.
The two days of the weekend are: Saturday and Sunday.
We saw our dog run into: the woods, the house, and the
Use a colon after the salutation of a business letter.
Use a colon between the hour and the minute of time.
It is now 4:22.
The train is due here at 5:08.
Use a colon between a title and a subtitle.
Mary Shelley wrote the novel Frankenstein: or, the Modern Prometheus.
Did William Shakespeare write Twelfth Night: Or What You Will?
The Beautiful Brazil
Worst Animated Movies Of All Time
Beautiful Steps on Earth
What to Eat in Meghalaya
Benefits of Pomelos
Weirdest Websites That Rock The Web
Mechanical Reversal of the Current
Magnets and Currents
: The Commutator
. It is not possible by hand to reverse the current with sufficient rapidity and precision to insure uninterrupted rotation; moreover, the physical exertion of such frequent reversals is considerable. Hence, some mechanical device for periodically reversing the current is necessary, if the motor is to be of commercial value.
The mechanical reversal of the current is accomplished by the use of the commutator, which is a metal ring split into halves, well insulated from each other and from the shaft. To each half of this ring is attached one of the ends of the armature wire. The brushes which carry the current are set on opposite sides of the ring and do not rotate. As armature, commutator, and shaft rotate, the brushes connect first with one segment of the commutator and then with the other. Since the circuit is arranged so that the current always enters the commutator through the brush B
, the flow of the current into the coil is always through the segment in contact with B
; but the segment in contact with B
changes at every half turn of the coil, and hence the direction of the current through the coil changes periodically. As a result the coil rotates continuously, and produces motion so long as current is supplied from without.
FIG. - The commutator.