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When measuring a large current flow should you use a shunt with zero resistance?
Wiki User
∙ 12y ago
It is not a shunt with zero resistance. It is very small, but it is not zero.
The large current develops a small voltage across the small resistance. Measuring that small voltage gives you a proportional measurement of the current.
Wiki User
∙ 12y ago
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Why does an ammeter have a low resistance while a voltmeter has high resistance?
I am going to assume that you mean low "resistance" in an open circuit test and are performing this with a multimeter. An ammeter works by place a very small amount of resistance in series with a circuit and then measuring the Voltage drop across the resistance. The Voltage is directly proportional to the current as given in ohms law: E = I x R If you are measuring the resistance through the ammeter it will have a very low resistance and impedance.
Why shunt resistance must be small in ammeter?
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
What is described as a device with specific resistance and is used to control current?
A current shunt is a device with a very low resistance, usually around one ohm. The exact resistance of the shunt is printed on the device for reference, and it is often slightly higher or lower than nominal, for example a 1 ohm shunt may actually have a resistance of .99986 ohms or 1.0002 ohms. A current shunt is not used to control current, however, so I do not know if this is the device you are asking about. It is used to measure current by using a precision voltmeter to measure the voltage drop across the shunt, and then using ohms law to calculate the current. Voltage (Volts) divided by Resistance (Ohms) equals Current (Amps). When the shunt is placed so that it interrupts a circuit, (placed in series), the current flowing in the circuit can be accurately measured with the shunt, without changing the values in the circuit enough to affect it. Many shunts of this type have a large heavy duty resistor that does not overheat easily. The shunt should also have a max current rating listed on it.
How do you calculate short circuit current?
A short circuit = 0 ohm, from this one can use ohms law to calculate the current, that is E/R voltage divided by resistance as in this instance your resistance is zero and you can't divide by zero so your current will be infinit. In other words if your power supply is large enough to supply 200 amp, your current on a short circuit will be 200 amp.
Why digital multimeter fails to read low resistance values?
They read low resistance values very well. I measured several dead shorts today accurately with a digital voltmeter. However, when attempting to measure LARGE amount of resistance, the current generator in a standard digital voltmeter may fail to effectively penetrate the medium being measured. It is for this reason that Meggers (Mega-Ohmmeters) are used to measure high amounts of resistance. They usually employ a hand crank to develop the current needed to effectively flow through the medium being measured. Sometimes digital voltmeters can be very inaccurate if they are measuring something that matches the impedance of the meter (loading effects of the voltmeter), but that is another story.
Is the open circuit voltage of a solar cell measured under non-illuminating condition?
Well, you should really measure the open-circuit voltage and the short circuit current both under dark and light conditions and then compare them to fully characterize a solar cell. Measuring the open-circuit voltage means measuring the voltage across the cell when no current is flowing (i.e., with a LARGE resistance as a load on the cell). Measuring the short-circuit current means measuring the current when the voltage across the circuit is essentially zero (i.e., with a VERY SMALL resistance as a load on the cell--thus, "short-circuit" current).
Why does an ammeter have a low resistance while a voltmeter has high resistance?
I am going to assume that you mean low "resistance" in an open circuit test and are performing this with a multimeter. An ammeter works by place a very small amount of resistance in series with a circuit and then measuring the Voltage drop across the resistance. The Voltage is directly proportional to the current as given in ohms law: E = I x R If you are measuring the resistance through the ammeter it will have a very low resistance and impedance.
Why do ammeter resistanse is very small?
An ammeter with a large resistance will affect the circuit that it is trying to measure. The ideal ammeter (or any measuring tool) should not affect what is being measured.
Can inserting a resistor in a circuit have an effect similar to an open circuit?
If the resistance is large enough, then there might not be enough voltage difference to allow much current. Since, Voltage = Current * Resistance, if resistance goes really large, and your voltage doesn't change, your current must decrease. An open circuit is where you do not have any current flowing, so whether no current verses very little current is the same is up to you.
Why shunt resistance is used ammeter?
A shunt resistance is a low resistance connected parallel to the galvanometer so that a large portion of current passes through the low resistance and a small fraction of current passes through the galvanometer this saves the galvanometer from damage
What is an amp meter used for?
This is used for just measuring the current... for large currents in tramsmission lines(busbars) current transformers are used.
What happens to current in a circuit if the voltage is halved and the resistance stays the same?
the current doubles.. explanation:V=IR hence I=V/R which means that when the supply voltage is constant ,current is inversely proportional to resistance.thus the current doubles. practically speaking when the resistance of the load(fan ,bulb,refrigerator,....) is less ,it draws more current from the source so as to balance the voltage across it.i.e; to maintain the voltage across it as constant. This answer is absolutely correct if you assume that the current comes from a pure voltage source ( voltage source with zero internal resistance). At the other extreme you could have a current source (such as a very large voltage source in series with a very large resistor), and then the current is practically independent of changes if the external resistance is changed (because the change represents a relatively minute change in the overall resistance). With appropriate circuitry it is possible to devise a situation where the current is practically independent of the changing resistance.
How does an AVO meter work to read resistance?
The AVO has a battery in it. Some AVOs have a 1.5 v battery plus a 15 v battery, used for measuring large resistances. The battery pushes current through the resistor being tested, and the meter measures the current. Because the battery voltage varies, you have to set the zero-ohm point by adjusting a control each time a resistance measurement is done.
Why shunt resistance must be small in ammeter?
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
What is electronic resister?
Electronics resistor are a basic passive element it oppose the flow of current . the opposition depend upon the value of that resistance high value resistance will only able to flow some few amount of current through them. but low value of resistance allow to flow large current through them.
What is lost volts?
A battery is rated to supply a certain number of volts. However, it actually supplies less, because they are "lost" as the current has to get out of the battery in the first place.(The battery has internal resistance)The amount of lost volts depends on the current being drawn:The less resistance a circuit has, the more current is drawn, because it's easier to flow.Example:If the circuit has little resistance, it draws a large current and the battery's internal resistance causes more lost volts.If the circuit has high resistance, it draws a small current and there are fewer lost volts.This is why when you short-circuit a battery (give it hardly any resistance to go through) it heats up and may explode. A large current is drawn and all the volts are used by the battery's internal resistance.
What is resistance of stator winding of induction motor?
Resistance of stator winding is the resistance of the copper conductors being used for building the windings of three separate phases, i.e. R-Y-B. These windings are marked like U1-U2, V1-V2 & W1-W2 at the motor terminals (6 nos.) for the three phases, i.e. R-Y-B respectively. We have simply to measure the resistance of each winding by using a multimeter by connecting the terminals (2 no.) to U1 & U2 and so on. The resistance should be in ohms not milliamps [amps is form of measuring current not resistance] milliamps to microamps in case of large motors, it may be in amps in case of small sized motors. But resistance of each winding should be nearly same to each other. This shows the electrical balance among windings & also proves the healthiness of the winding.
