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Why should the resistance of ammeter be small and that of voltmeter be large? |
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Answer» An\xa0ammeter\xa0has to measure to current flowing through the circuit. Resistance offers an obstruction to the current flow. So, if the resistance of an ammeter is large , the current measured by the ammeter will be quite less as compared to the actual amount of current flowing through the circuit which is undesirable. If ammeter has\xa0zero resistance\xa0, then it will give the exact value of current. But this is not practically possible because every material has some value of\xa0internal resistance\xa0which we can\'t control. For this reason , ammeter must have small resistance Voltmeters\xa0are put in parallel with the load in order to measure the\xa0potential differencebetween two *different* points.\xa0If they are in parallel with the load, then at the first junction the current will split and flow into both paths (Kirchhoff\'s Laws). However, if current is flowing through the voltmeter, then it is not all flowing through the load, and the potential difference across the load would change when the voltmeter is added and removed. This is unfavourable. Therefore, the voltmeter must have a very high resistance so that current doesn\'t flow through it.\xa0 Find video lessons, notes, papers, syllabus, solutions to doubts & more User profile imageLogin / Sign UpHomeClass 1 to 12JEENEETDoubt and SolutionsTextbook SolutionsBoard PapersSample PapersPricingDiagnostic TestB2B PartnersFranchiseeTopper TVTopperlearning CBSE Class 10 - Ask The ExpertAnsweredWhy should the resistance of : a)an ammeter be very small? b)a voltmeter be very large?Asked by | 30th Apr, 2012, 11:09: PMExpert Answer:An ammeter has to measure to current flowing through the circuit. Resistance offers an obstruction to the current flow. So, if the resistance of an ammeter is large , the current measured by the ammeter will be quite less as compared to the actual amount of current flowing through the circuit which is undesirable. If ammeter has zero resistance , then it will give the exact value of current. But this is not practically possible because every material has some value of internal resistance which we can\'t control. For this reason , ammeter must have small resistance Voltmeters are put in parallel with the load in order to measure the potential differencebetween two *different* points. If they are in parallel with the load, then at the first junction the current will split and flow into both paths (Kirchhoff\'s Laws). However, if current is flowing through the voltmeter, then it is not all flowing through the load, and the potential difference across the load would change when the voltmeter is added and removed. This is unfavourable. Therefore, the voltmeter must have a very high resistance so that current doesn\'t flow through it |
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