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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.
Wiki User
∙ 13y ago
Wiki User
∙ 13y agoIdeal current measuring instrument should have zero resistance.
The ammeter is added in series and hence it should not load the circuit.
Voltmeter on other hand should have infinite impedance so that it can used at places where current is very low.
Wiki User
∙ 14y agoAn 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.
Wiki User
∙ 14y agoTypically commercial testers were designed for an output impedance of 11 megohm.
Wiki User
∙ 11y agoAs little as possible, since the ammeter must be inserted in the circuit,
and the current it measures must flow through it.
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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.
Why is ideal resistance of a voltmeter infinity?
generally voltmeters are connected in parallel in the circuit.If the voltmeter resistance is lower as it increases the current rating,because by connecting parallel we are decreasing the resistance,so if the voltmeter resistance is not too much higher it leads to burning of the meter,For that we can conclude that the in ideal the voltmeter has infinite resistance.
What is the ideal voltmeter high or low?
Ideal Voltmeter has an infinite resistance so it won't draw current from the circuit, but in real life ideal voltmeter doesn't exist.
What should be the resistance of an ideal voltmeter?
infinity- so that all the voltage is measured across the component instead of losing some in voltometer circuitry
Ideal universal high resistance voltmeter?
The ideal, or theoretical, voltmeter has infinite resistance, which means that, at any measured voltage, there is no current through the voltmeter. In the practical world, this is impossible, but there are high resistance voltmeters that minimize the error introduced by drawing a current from a circuit. A typical digital voltmeter has 10 to 20 megohms of resistance, and there are high performance versions that can have thousands of megohms of resistance, or more.
How would you extend the range of a voltmeter and ammeter?
if we would like to expand the range of voltmeter we should change the voltmeter resistance even to be appropriate . we should use a variable resistance to control of its value . I would extend the range of a voltmeter by adding resistance in series with it. I would extend the range of an ammeter by connecting resistance in paerallel with it.
How is resistivity connected to resistance?
Resistance is connected in parallel with voltmeter or say, voltmeter is connected in parallel with resistance.
Battery connected to high Resistance voltmeter the reading is 1.5V when it is shorted on a low resistance ammeter the current is 2.5A what is the emf and the internal resistance of the battery?
The Thevenin equivalent circuit of this battery is 1.5V and 0.6 ohms in series. A more exact answer cannot be given without knowing the actual resistance of the 2 meters (I assumed infinite for the voltmeter and zero for the ammeter, as would be for ideal meters).However I would NEVER attempt this test as you describe it, many types of batteries will explode like bombs when shorted (as they would be when an ammeter was placed across them)! The correct way to do this test safely is with just a voltmeter and an adjustable high wattage resistor.
Why do you get different results when calculating the voltage drop across a resistor and ignoring resistance of a voltmeter and when considering it?
Voltage drop is the product of current and resistance. When you connect a voltmeter across a resistor, you are connecting that voltmeter's internal resistance in parallel with that resistor. The resulting resistance of this parallel combination is lowerthan that of the resistor. As a result the voltage drop (current times this lower resistance) will be lower than it would be without the voltmeter connected. This is called the 'loading effect' of that voltmeter.The higher the internal resistance of the voltmeter, the less effect it will have on lowering the overall resistance when connected across a resistor. This is why the internal resistance of a voltmeter is made deliberately very high. Under most circumstances, therefore, a conventional voltmeter will have very little effect on the resistance of the circuit being tested and, so, it will have no significant effect on the voltage appearing across the resistor.However... for circuits that already have exceptionally-high resistance values, you must be careful when you select a voltmeter as you must take into account its internal resistance and ensure the voltmeter you use has the very highest internal resistance available. This is because the loading effect increases with circuits that have a high resistance. That might involve selecting a voltmeter that works on a completely-different principle , such as an electrostatic voltmeter or, perhaps, an oscilloscope
Why there is an extension range of voltmeter when a series resistance not equal to voltmeter is used?
why is extention
Why do you have specific resistance combination inside a voltmeter and an ammeter Explain?
in voltmeter we have internal Resistance and connected in series , to current don't transfer in voltmeter , and we have internal resistance in ammeter and connected in parallel , to most current transfer through the ammeter.
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.
