The voltage across a voltmeter Olymp 09

In summary: The best we can do is use the voltmeter to measure the terminal voltage of the battery, which means it's the scalar addition of two potentials that we measure here.
  • #1
Entanglement
439
13
ImageUploadedByPhysics Forums1402164069.874746.jpg


The question I'm asking about is Olymp 09

My attempt : 2.36 V

Vb1 / (R + r1 + r2) = 2 / 2.5 = 0.8 A
Vb2 / (R + r1 + r2) = 5 / 2.5 = 2 A

The reading of the voltmeter = the voltage across r1 + the voltage across r2 and R = (0.8)(2.2) + (2)(0.3)
= 2.36 V

I'm not sure of my answer, and even if it's correct I'm not completely convinced how is my solution is right.
 
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  • #2
The voltmeter sits across a 2V battery. What do you suppose it will read?
 
  • #3
rude man said:
The voltmeter sits across a 2V battery. What do you suppose it will read?
Not 2 V, as we have to consider the internal resistances.

@ElmorshedyDr: What is meant with "in the opposite circuit [...]"?
I don't understand your approach to convert those currents to voltages across the 0.3 Ohm resistor.
 
  • #4
mfb said:
Not 2 V, as we have to consider the internal resistances.

Right. Didn't see that.
 
  • #5
So the answer is voltmeter reading = VB + V across the internal resistance = 2 + (1.2)(0.3) = 2.36 V ??
 
  • #6
ElmorshedyDr said:
So the answer is voltmeter reading = VB + V across the internal resistance = 2 + (1.2)(0.3) = 2.36 V ??

Correct.
 
  • #7
ElmorshedyDr said:
View attachment 70418

The question I'm asking about is Olymp 09

My attempt : 2.36 V

Vb1 / (R + r1 + r2) = 2 / 2.5 = 0.8 A
Vb2 / (R + r1 + r2) = 5 / 2.5 = 2 A

The reading of the voltmeter = the voltage across r1 + the voltage across r2 and R = (0.8)(2.2) + (2)(0.3)
= 2.36 V

I'm not sure of my answer, and even if it's correct I'm not completely convinced how is my solution is right.
Your working is basically correct, but your technique is not what I was expecting. Can you explain the method you have used?
 
  • #8
rude man said:
Correct.
But I'm still confused, why can't we just calculate the total voltage and the total resistance and then find the total current ad multiply it by the internal resistance of B1 to find the reading, since it is connected in parallel with internal resistance of the battery which would be 0.36V
 
  • #10
ElmorshedyDr said:
But I'm still confused, why can't we just calculate the total voltage and the total resistance and then find the total current ad multiply it by the internal resistance of B1 to find the reading, since it is connected in parallel with internal resistance of the battery which would be 0.36V
That can't be correct because the voltmeter is not connected directly across the internal resistance of the battery. The voltmeter reading is the sum of two voltages---you can see how it also captures the battery's EMF.

The best we can do is use the voltmeter to measure the terminal voltage of the battery, which means it's the scalar addition of two potentials that we measure here.

I'm stll interested in your explanation of the first method you showed. It is correct, BTW.
 

1. What is a voltmeter and how does it measure voltage?

A voltmeter is an instrument used to measure the voltage or potential difference between two points in an electrical circuit. It works by connecting two probes to the points of interest, and the voltage is shown on a digital or analog display.

2. How is the voltage across a voltmeter Olymp 09 different from other voltmeters?

The voltage across a voltmeter Olymp 09 is not significantly different from other voltmeters. It is simply a model or brand name of a voltmeter, and its accuracy and features may vary depending on the specific model.

3. Can a voltmeter be used to measure current or resistance?

No, a voltmeter is specifically designed to measure voltage. To measure current, an ammeter should be used, and to measure resistance, an ohmmeter is needed. Attempting to measure current or resistance with a voltmeter can damage the instrument and give inaccurate readings.

4. What is the range of voltages that can be measured with a voltmeter Olymp 09?

The range of voltages that can be measured with a voltmeter Olymp 09 will vary depending on the specific model. Some may have a smaller range, such as 0-10 volts, while others may have a wider range, such as 0-1000 volts. It is important to check the specifications of the specific model to determine its voltage range.

5. How can the accuracy of a voltmeter Olymp 09 be ensured?

The accuracy of a voltmeter Olymp 09 can be ensured by regularly calibrating it. This involves comparing its readings to a known and precise voltage source. If any discrepancies are found, the voltmeter may need to be adjusted or repaired. It is also important to handle the voltmeter carefully and avoid any physical damage that may affect its accuracy.

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