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The theoretical resistance (idea resistance) of an ammeter is zero. With a voltmeter, it's infinitely high.
In some analog meters the full scale deflection is produced by only about 50 microamps. Actually that does not change from ammeter to voltmeter, just the configuration of the meter's external "connection circuit"changes.
Simple ammeters are 'connected in series' devices. The resistance of such an ammeter must be kept very low because, if it were a high resistance, that would seriously limit the current allowed into the circuit and would impair the circuit's function.
Voltmeters are 'connected in parallel' devices. The theoretical resistance of a volt meter is very high, the higher the better. It is checking the potential between two points, so, to have the least effect on the circuit it is measuring, it must draw as little current as possible.
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MaxineAn IDEAL voltmeter would measure the voltage at the test point without becoming a part of the circuit. The only way to not become any part of the circuit at all is to have an infinite resistance, in other words, infinity Ohms. (In the case of an alternating current, substitute the word impedance for resistance, above.) Neither a total vacuum nor any physical material exhibits infinite resistance, so there is no such thing as an IDEAL voltmeter. Further, it would be difficult to transmit an electrical signal across a test probe with an infinite resistance, so again, no such thing.
In my opinion, a QUALITY voltmeter has a impedance of 10 million (10M) Ohms or more.
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Why voltmeter should have a very high resistance?
well a voltmeter measures AC and DC voltage. resistance is a term used only for DC voltage, A voltmeter uses a term called Impedance for AC, without it, when you measure across two terminals it would create a short circuit and would blow up the meter. it is basically a safety feature to prevent people from creating short circuits when measuring.
What is the use of universal high resistance voltmeter?
A voltmeter must have a very high resistance to measure voltage. A voltmeter is placed in parallel with the element that you are measuring. If the voltmeter has a low internal resistance, then all of the current will flow through the voltmeter instead of the element. You want all of the current to flow through the element, to get an accurate reading of the voltage. Conversely, an ampmeter must have zero resistance, because it is placed in series with the element.
What will happen if a voltmeter has a low shunt resistance instead of having high shunt resistance?
The purpose of a voltmeter is to indicate the potential difference between two points in a circuit.When a voltmeter is connected across a circuit, it shunts the circuit. If the voltmeter has a low resistance,it will draw a substantial amount of current. This action lowers the effective resistance of the circuit andchanges the voltage reading.
What resistance value is add to convert a galvanometer into a voltmeter?
It depends on the resistance of the galvanometer and the current required to reach full scale. A 100 ohm meter requiring 1 milliampere would require 99.9 KOhms in series to become a 100 volt voltmeter.
What is loading affect of multimeter?
'Loading effect' applies to voltmeters, or to multimeters when set to measure voltage. It describes the change in a circuit's resistance when the resistance of the voltmeter is taken into account. It's effect is to cause the resulting measuredvoltage to be different from the actual voltage which would appear without the voltmeter connected. The loading effect is minimised by ensuring that the internal resistance of the voltmeter is significantly higher than the resistance of that part of the circuit to which it is connected. For general voltage measurement, this is usually the case anyway, but when measuring circuits which, themselves, have very high resistance care must be taken over the choice of voltmeter to be used.
