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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.
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Why is the resistance of volt meter very high?
So it doesn't effect the circuit being tested. If a low impediance or resistance meter were inserted in the circuit, voltages may drop and effect the accuracy of the test. Any voltmeter will use some power from the circuit to make a reading. A "high impediance voltmeter" will use very little power from the circuit so the voltage reading will be as accurate as it can be.
How do you measure the resistance of a motor?
we can measure the resistance of the motor by using voltmeter ammeter method of by directly using a multimeter across the armature terminals of the motor in voltmeter ammeter method we should use a less value of dc voltage to find the resistance
How do you find the voltage drop over a resistor?
To find the voltage drop over a resistor, you measure it with a voltmeter connected across the resistor. You also need to make sure the impedance of the voltmeter is high enough to not shift the effective resistance more than the required accuracy of the measurement.
How do you convert voltmeter to ohmmeter?
First you will need a constant current source. Do NOT connect the voltmeter to the constant current source without the resistor to be measured already connected. Do NOT use a battery, it is a voltage source. Then follow these steps to measure a resistor:connect the voltmeter across the resistor to be measuredconnect the voltmeter-resistor combination across the constant current sourceread the voltmeter and record the voltagedisconnect the voltmeter-resistor combination from the constant current sourcedisconnect the voltmeter from the resistorcalculate the resistance from the measured voltage and current from the source with Ohm's law in this form: R = V ÷ IIts much easier to just use the ohms setting on a multimeter.
What is the difference between ammeters and amp meters?
An Ammeter connects a low impedance on the test points, so the equivalent of that is a "short circuit" between the test points. This is done to avoid a drop of current on the tested circuit. A Voltmeter connects a high impedance on the test points, so the equivalent of that is a "open circuit" between the test points. This is done to avoid a drop of voltage on the tested circuit. --------- In terms of external connections Ammeter (used to measure current) is connected in series of the circuit (through which the current flow need to be measured) and voltmeter (used to measure voltage) is connected in parallel to points in circuit (across which voltage needs to be measured).
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
How do design a high voltage voltmeter?
Use a voltage divider and an standard high input impedance voltmeter connected to the low voltage output tap of the divider. Just check that: a) the voltage divider has enough resistance to minimize loading of the voltage source (The voltage divider resistance should be as high as possible). b) the voltmeter's input impedance is at least 10-20 times larger than the output resistance (impedance) of the divider. If necessary add a high-input impedance amplifier or a transducer between the divider output and the voltmeter. What is high voltage for you?
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.
Why is the resistance of volt meter very high?
So it doesn't effect the circuit being tested. If a low impediance or resistance meter were inserted in the circuit, voltages may drop and effect the accuracy of the test. Any voltmeter will use some power from the circuit to make a reading. A "high impediance voltmeter" will use very little power from the circuit so the voltage reading will be as accurate as it can be.
How do you measure the resistance of a motor?
we can measure the resistance of the motor by using voltmeter ammeter method of by directly using a multimeter across the armature terminals of the motor in voltmeter ammeter method we should use a less value of dc voltage to find the resistance
What device is used to measure the resistance of a resistor?
You can use a multi-meter to measure resistance. The specific portion of the meter for measuring resistance is called an ohmmeter.
How is voltage measured?
Use a voltmeter with a high input impedance and measure at the source the voltage.
How come when you use a voltmeter the applied voltage is not equal to the individual voltage of a resistor when it should be because it's in parallel I got 2.5 V in the applied v but only 2 v in each?
There are two possible explanations... The resistance of the applied voltage is sufficiently high, in comparision with the resistors, to cause the resistors to pull the voltage down. The resistance of the voltmeter is sufficiently low, in comparision with the resitors, to cause the voltmeter to pull the voltage down.
How do you determine the emf and internal resistance of a cell?
You can measure the emf of a cell by using a voltmeter, as this draws current from a cell. You can use the voltage, the emf, and the load resistance to determine the internal resistance of the cell.
Why the series resistor of the voltmeter is high?
Aim of any measuring instrument is to measure the object without affecting it. Voltmeter is used to measure voltage between two points and connected in parallel. Thus voltmeter should not change the voltage. If voltmeter resistance is very high, it will be as good as infinity compared to load. Thus connecting voltmeter will not change the voltage and measure it accurately.
How do you find the voltage drop over a resistor?
To find the voltage drop over a resistor, you measure it with a voltmeter connected across the resistor. You also need to make sure the impedance of the voltmeter is high enough to not shift the effective resistance more than the required accuracy of the measurement.
What methods would you use to test the resistance of a long and short wire?
By placing a voltmeter either side you can see how much electricity goes through the wire. This is because a voltmeter measures the difference in volts.
