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if so and if not

We can use these expressions instead of repeating a verb that has already been mentioned.
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  • 'copula1 verbs
  • 'social' language
  • (a) few and (a) little
  • (a)round and about
  • (be) used to + noun or... -ing
  • (Great) Britain, the United Kingdom, the British Isles and England
  • -ing form ('gerund')
  • -ing form after to
  • -ing form or infinitive?
  • abbreviations
  • about to
  • above and over
  • across and over
  • across and through
  • active verb forms
  • actual(ly)
  • adjectives ending in -Iy
  • adjectives without nouns
  • adjectives: order
  • adjectives: position
  • adverbs of manner
  • adverbs: position (details)
  • adverbs: position (general)
  • after (conjunction)
  • after (preposition); afterwards (adverb)
  • after all
  • afternoon, evening and night
  • ages
  • ago
  • all (of) with nouns and pronouns
  • all and every
  • all and whole
  • all right
  • all with verbs
  • all, everybody and everything
  • almost and nearly
  • also, as well and too
  • although and though
  • among and between
  • and
  • and after try, wait, go etc
  • another
  • any (= 'it doesn't matter which')
  • any and no: adverbs
  • appear
  • articles: a and an; pronunciation of the
  • articles: a/an
  • articles: countable and uncountable nouns
  • articles: introduction
  • articles: special rules and exceptions
  • articles: talking in general
  • articles: the
  • articles: the difference between a/an and the
  • as and like
  • as if and as though
  • as much/many ... as ...
  • as well as
  • as, because and since (reason)
  • as, when and while (things happening at the same time)
  • as...as ...
  • ask
  • at all
  • at, in and on (place)
  • at, in and on (time)
  • be + infinitive
  • be with auxiliary do
  • be: progressive tenses
  • because and because of
  • before (adverb)
  • before (conjunction)
  • before (preposition) and in front of
  • begin and start
  • big, large, great and tall
  • born
  • borrow and lend
  • both (of) with nouns and pronouns
  • both with verbs
  • both... and...
  • bring and take
  • British and American English
  • broad and wide
  • but = except
  • by: time
  • can and could: ability
  • can and could: forms
  • can with remember, understand, speak, play, see, hear, feel, taste and smell
  • can: permission, offers, requests and orders
  • can: possibility and probability
  • close and shut
  • come and go
  • comparison: comparative and superlative adjectives
  • comparison: comparative and superlative adverbs
  • comparison: much, far etc with comparatives
  • comparison: using comparatives and superlatives
  • conditional
  • conjunctions
  • contractions
  • countable and uncountable nouns
  • country
  • dare
  • dates
  • determiners
  • discourse markers
  • do + -ing
  • do and make
  • do: auxiliary verb
  • during and for
  • during and in
  • each and every
  • each other and one another
  • each: grammar
  • either... or...
  • either: determiner
  • ellipsis (leaving words out)
  • else
  • emphasis
  • emphatic structures with it and what
  • enjoy
  • enough
  • even
  • eventual(ly)
  • ever
  • every and every one
  • except
  • except and except for
  • exclamations
  • excuse me, pardon and sorry
  • expect, hope, look forward, wait, want and wish
  • explain
  • fairly, quite, rather and pretty
  • far and a long way
  • farther and further
  • fast
  • feel
  • fewer and less
  • for + object + infinitive
  • for, since, from, ago and before
  • for: purpose
  • future perfect
  • future progressive
  • future: introduction
  • future: present progressive and going to
  • future: shall and will (interpersonal uses)
  • future: shall/will (predictions)
  • future: simple present
  • gender (masculine and feminine language)
  • get (+ object) + verb form
  • get + noun, adjective, adverb particle or preposition
  • get and go: movement
  • go ... -ing
  • go meaning'become'
  • go: been and gone
  • had better
  • half (of)
  • hard and hardly
  • have (got) to
  • have (got): possession, relationships etc
  • have + object + verb form
  • have: actions
  • have: auxiliary verb
  • have: introduction
  • hear and listen (to)
  • help
  • here and there
  • holiday and holidays
  • home
  • hope
  • how and what... like?
  • if only
  • if so and if not
  • if-sentences with could and might
  • if: ordinary tenses
  • if: special tenses
  • ill and sick
  • imperative
  • in and into (prepositions)
  • in case
  • in spite of
  • indeed
  • infinitive after who, what, how etc
  • infinitive of purpose
  • infinitive without to
  • infinitive: negative, progressive, perfect, passive
  • infinitive: use
  • instead of... -ing
  • inversion: auxiliary verb before subject
  • inversion: whole verb before subject
  • irregular verbs
  • it's time
  • it: preparatory object
  • it: preparatory subject
  • last and the last
  • let's
  • letters
  • likely
  • long and for a long time
  • look
  • look (at), watch and see
  • marry and divorce
  • may and might: forms
  • may and might: permission
  • may and might: probability
  • mind
  • modal auxiliary verbs
  • more (of): determiner
  • most (of): determiner
  • much (of), many (of): determiners
  • much, many, a lot etc
  • must and have to; mustn't, haven't got to, don't have to, don't need to and needn't
  • must: deduction
  • must: forms
  • must: obligation
  • names and titles
  • nationality words
  • need
  • negative questions
  • negative structures
  • neither (of): determiner
  • neither, nor and not... either
  • neither... nor...
  • next and nearest
  • next and the next
  • no and none
  • no and not
  • no and not a/not any
  • no more, not any more, no longer, not any longer
  • non-progressive verbs
  • noun + noun
  • numbers
  • once
  • one and you: indefinite personal pronouns
  • one: substitute word
  • other and others
  • ought
  • own
  • participle clauses
  • participles used as adjectives
  • participles: 'present' and 'past' participles (-ing and -ed)
  • passive structures: introduction
  • passive verb forms
  • past tense with present or future meaning
  • past time: past perfect simple and progressive
  • past time: past progressive
  • past time: present perfect progressive
  • past time: present perfect simple
  • past time: simple past
  • past time: the past and perfect tenses (introduction)
  • perfect tenses with this is the first time..., etc
  • personal pronouns (I, me, it etc)
  • play and game
  • please and thank you
  • possessive with determiners (a friend of mine, etc)
  • possessive's: forms
  • possessive's: use
  • possessives: my and mine, etc
  • prepositional verbs and phrasal verbs
  • prepositions after particular words and expressions
  • prepositions and adverb particles
  • prepositions at the end of clauses
  • prepositions before particular words and expressions
  • prepositions: expressions without prepositions
  • present tenses: introduction
  • present tenses: present progressive
  • present tenses: simple present
  • progressive tenses with always
  • punctuation: apostrophe
  • punctuation: colon
  • punctuation: comma
  • punctuation: dash
  • punctuation: quotation marks
  • punctuation: semi-colons and full stops
  • question tags
  • questions: basic rules
  • questions: reply questions
  • questions: word order in spoken questions
  • quite
  • real(ly)
  • reflexive pronouns
  • relative pronouns
  • relative pronouns: what
  • relative pronouns: whose
  • relatives: identifying and non-identifying clauses
  • remind
  • reported speech and direct speech
  • reported speech: orders, requests, advice etc
  • reported speech: pronouns; 'here and now' words; tenses
  • reported speech: questions
  • requests
  • road and street
  • say and tell
  • see
  • seem
  • shall
  • short answers
  • should
  • should after why and how
  • should and would
  • should, ought and must
  • should: (If I were you) I should ...
  • similar words
  • since (conjunction of time): tenses
  • singular and plural: anybody etc
  • singular and plural: irregular plurals
  • singular and plural: plural expressions with singular verbs
  • singular and plural: pronunciation of plural nouns
  • singular and plural: singular words ending in -s
  • singular and plural: singular words with plural verbs
  • singular and plural: spelling of plural nouns
  • slow(ly)
  • small and little
  • smell
  • so am I, so do I etc
  • so and not with hope, believe etc
  • some and any
  • some/any and no article
  • some: special uses
  • somebody and anybody, something and anything, etc
  • sound
  • spelling and pronunciation
  • spelling: -ise and -ize
  • spelling: -ly
  • spelling: capital letters
  • spelling: ch and tch, k and ck
  • spelling: doubling final consonants
  • spelling: final -e
  • spelling: full stops with abbreviations
  • spelling: hyphens
  • spelling: ie and ei
  • spelling: y and i
  • still, yet and already
  • subject and object forms
  • subjunctive
  • such and so
  • suggest
  • surely
  • sympathetic
  • take
  • take (time)
  • tall and high
  • taste
  • telephoning
  • telling the time
  • tenses in subordinate clauses
  • that: omission
  • the same
  • there is
  • think
  • this and that
  • too
  • travel, journey and trip
  • unless and if not
  • until and by
  • until and to
  • used to + infinitive
  • verbs with object complements
  • verbs with two objects
  • way
  • weak and strong forms
  • well
  • when and if
  • whether and if
  • whether... or...
  • which, what and who: question words
  • who ever, what ever, how ever etc
  • whoever, whatever, whichever, however, whenever and wherever
  • will
  • wish
  • worth ... -ing
  • would
  • would rather
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  • Electricity

    Electric charge

    The presence of charge gives rise to an electrostatic force charges exert a force on each other, an effect that was known, though not understood, in antiquity.A lightweight ball suspended from a string can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms. This discovery led to the well known axiom like charged objects repel and opposite charged objects attract.

    The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulombs law, which relates the force to the product of the charges and has an inverse square relation to the distance between them.The electromagnetic force is very strong, second only in strength to the strong interaction, but unlike that force it operates over all distances.In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 1042 times that of the gravitational attraction pulling them together.

    Study has shown that the origin of charge is from certain types of subatomic particles which have the property of electric charge. Electric charge gives rise to and interacts with the electromagnetic force, one of the four fundamental forces of nature. The most familiar carriers of electrical charge are the electron and proton. Experiment has shown charge to be a conserved quantity, that is, the net charge within an isolated system will always remain constant regardless of any changes taking place within that system.within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire.2 5 The informal term static electricity refers to the net presence or imbalance of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other.

    The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative, and that by protons positive, a custom that originated with the work of Benjamin Franklin.The amount of charge is usually given the symbol Q and expressed in coulombs;each electron carries the same charge of approximately ?1.6022?10?19 coulomb. The proton has a charge that is equal and opposite, and thus +1.6022?10?19 coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle.

    Charge can be measured by a number of means, an early instrument being the gold leaf electroscope, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer.


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