- #1
labview1958
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I have set up an apparatus to find the Null point with a galvanometer. I am unable to find one as the galvanometer always points to the right, no matter what. Help anyone?
Finding the Null Point with a Galvanometer: Advice Needed
- Thread starter labview1958
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- Galvanometer Point
In summary, the conversation is about setting up an apparatus to find the Null point with a galvanometer. However, the person is unable to find one as the galvanometer always points to the right. Another person suggests checking the wiring and provides diagrams to show the correct way to connect a potentiometer. It is also mentioned that the system should not be left running for too long as one of the cells may become exhausted. The conversation ends with the person still unable to find the null point and unsure about the voltage readings of the cells.
- #2
Studiot
- 5,440
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If the meter points in the same direction at both ends of the adjustment range you will not find a null so check your wiring. That is the usual reason.
- #3
labview1958
- 37
- 0
The wirings are correct. Here is the circuit.
http://i1233.photobucket.com/albums/ff387/labview1958/th_Clip2.jpg?t=1299755747
http://i1233.photobucket.com/albums/ff387/labview1958/th_Clip2.jpg?t=1299755747
- #4
Studiot
- 5,440
- 9
It's very hard to make out your circuit since you only posted the thumbnail.
In the interests of progress I have made some sketches because I think you are connecting the potentiometer or slide wire incorrectly.
There are two ways to connect a pot. As a variable resistor and as a potentiometer.
I have shown the variable resistor connection in Fig5 and I think this is what you are doing incorrectly.
You need the potentiometer connection as in Fig1. Note the slide wire or outer (end) terminals of the pot are connected directly across the battery.
The (variable) output voltage is taken from the third terminal or slider.
You can now compare this voltage with another one as in Fig2. The second voltage can be derived from the same battery or a different one. That is why I have shown the connection dotted.
When the voltages are the same, a centre zero meter connected between them will read zero.
Figs3 and 4 show the conditions for the meter to swing left and right.
go well
In the interests of progress I have made some sketches because I think you are connecting the potentiometer or slide wire incorrectly.
There are two ways to connect a pot. As a variable resistor and as a potentiometer.
I have shown the variable resistor connection in Fig5 and I think this is what you are doing incorrectly.
You need the potentiometer connection as in Fig1. Note the slide wire or outer (end) terminals of the pot are connected directly across the battery.
The (variable) output voltage is taken from the third terminal or slider.
You can now compare this voltage with another one as in Fig2. The second voltage can be derived from the same battery or a different one. That is why I have shown the connection dotted.
When the voltages are the same, a centre zero meter connected between them will read zero.
Figs3 and 4 show the conditions for the meter to swing left and right.
go well
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- #5
labview1958
- 37
- 0
Here is my circuit. Still cannot find null point.
http://i1233.photobucket.com/albums/ff387/labview1958/Clip2.jpg
http://i1233.photobucket.com/albums/ff387/labview1958/Clip2.jpg
- #6
Studiot
- 5,440
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Is L0 a slide wire and does the arrow mean the slider?
- #7
labview1958
- 37
- 0
Yes. I manage to get the null point for about 10 minutes. I switch off for about 5 minutes. After that I never ever got back the null point. Can help?
- #8
Studiot
- 5,440
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I guess one of your cells is exhausted after 10 minutes.
You are not meant to let the system run for that long.
You are not meant to let the system run for that long.
- #9
labview1958
- 37
- 0
I checked their voltage. The reading was 1.5V for the dry cell and 6V for the driver cell. I am really lost.
1. How do I use a galvanometer to find the null point?
To find the null point with a galvanometer, you will need to connect it in a circuit with a known resistor and a variable resistor. Adjust the variable resistor until the galvanometer reads zero, indicating that the current passing through the known resistor is balanced.
2. What is the significance of finding the null point with a galvanometer?
The null point is the point at which the current in a circuit is balanced, meaning there is no net flow of electricity. This can be useful in determining the resistance of a known resistor or in measuring small changes in current.
3. Can I use a galvanometer to find the null point in any circuit?
No, a galvanometer can only be used to find the null point in a circuit where the current is being measured. This means that the circuit must have a known resistor and a variable resistor for the galvanometer to be effective.
4. How do I know if I have found the true null point?
The true null point is when the galvanometer reads exactly zero. However, due to small imperfections in the circuit and the galvanometer, it may not be possible to achieve a perfect null point. In this case, you should aim for the closest reading to zero as possible.
5. Are there any safety precautions I should take when using a galvanometer?
Yes, it is important to always use the appropriate amount of voltage and current for your galvanometer. Exceeding these limits can damage the instrument and potentially cause injury. It is also important to handle the galvanometer carefully as it is a sensitive piece of equipment.
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