Conversion of Galvanometer to Ammeter

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Homework Help Overview

The discussion revolves around the conversion of a galvanometer into an ammeter using a shunt resistance to measure high currents. Participants explore the implications of measuring a fraction of the total current and how this relates to practical applications in electrical measurements.

Discussion Character

  • Conceptual clarification, Assumption checking, Exploratory

Approaches and Questions Raised

  • Participants discuss the rationale behind using a shunt to measure large currents and question how to interpret the measurements from the galvanometer. Some express confusion about how to calculate the total current from the measured value, while others clarify that the shunt allows for a known portion of the current to be measured.

Discussion Status

The conversation is ongoing, with some participants providing insights into the practicality of using shunts and the convenience of measuring different current ranges. However, questions remain about the possibility of decreasing the range of an ammeter, with differing opinions noted among participants.

Contextual Notes

There is mention of a book stating that the range of an ammeter cannot be decreased, contrasting with a mentor's perspective that suggests the range can be increased. This indicates a potential area of misunderstanding or differing interpretations among participants.

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This is kind of a stupid question but...to measure high currents, a galvanometer is connected parallel to a shunt resistance so that most of the current passes through the shunt resistance but only a small amount of current passes through the galvanometer. But wouldn't this defeat the purpose of measuring a large current? Since only a small current is being measured. :|
 
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Think of it as measuring a known portion of the current. Anyway, you can easily figure out what the large current is from the measurement. When measuring the current in a power line, it is very inconvenient and costly to flow the entire current (at a high voltage) through your meter.

Pretty much all Ammeters are actually galvanometers with a shunt. Or galvanometers connected to coils to measure the magnetic field caused by the current.
 
How would you figure out the larger current? Won't the values of the two be different?

Sorry, I'm a little confused here
 
Say you have a galvanometer with a resistance of 1 ohm. You make your shunt 1 ohm as well. Then half of the current goes each way. Your meter measures half the current, so you multiply it by 2 to get the whole current. Usually the shunt resistance is made smaller so only a tenth, hundredth or thousandth of the current goes through the meter.
 
Oh, I get it now. Thanks!
 
Most welcome! I forgot to mention convenience. When you need a meter to measure current, you don't need to order one specifically for the range required. Any meter will work with the correct shunt. A meter with multiple current ranges just switches in different shunts. Very handy!
 
can the range of an ammeter be decreased ?
@Delphi51 in the above comment you said that we don't need ammeter of a particular range . i comprehend that as by connecting a shunt the range can be increased . but for a given purticular ammeter is there any way that the range might be decreased ... i referred a book which says that the range can never be decreased but one of my mentors says that the range can be increased . HELP
 
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