Is the Internal Resistance of the Voltmeter Accurate in Series Circuit?

In summary, two resistors with values of 600 Ω and 400 Ω are connected in series and supplied with 90 V. A voltmeter connected to the 600 Ω resistor shows a reading of 60 V, which is impossible. The attempt at a solution was to use the equation V = IR to find the internal resistance of the voltmeter, but the book states an internal resistance of 3000 Ω. Further discussion includes the possibility of the book being incorrect and the need to draw a circuit diagram for a clearer understanding.
  • #1
kliker
104
0

Homework Statement


a resistor of 600 Ω and one of 400 Ω are connected in series and their combination is being supplied by 90 V. A voltmeter that is connected on edge of the resistor of 600 Ω shows 60 V. a) what's the internal resistance of the voltmeter.


The Attempt at a Solution



i found the real V in the resistor of 600 V which is 54 V. But the voltmeter shows 60 V. Now I don't know how is this possible

if they are in parallel could we just find the Rtot that will be Rv* Rs/(Rv+Rs) and then say I = V/R

and from this equation find the Rv? but i find false results using this method, the book says 3000 Ω
 
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  • #2
The voltmeter reads 50 V if its internal resistance is 3000 ohm. 60 V is impossible.

ehild
 
  • #3
ehild said:
The voltmeter reads 50 V if its internal resistance is 3000 ohm. 60 V is impossible.

ehild

hm, so the book has it wrong?

Im using the university physics by Hugh D. Young it's in chapter 27

never mind, let's suppose that it reads 50, how can I find the resistance of the voltmeter? There isn't any method inside the book, and our teacher never explained us anything like that, I'm just curious how this can be solved

thanks in advance
 
  • #4
Draw the circuit diagram first. Show me, please.

ehild
 

1. What is the resistance of a voltmeter?

The resistance of a voltmeter is typically very high, ranging from 10,000 ohms to 1,000,000 ohms. This is necessary in order to prevent the voltmeter from drawing too much current from the circuit and altering the voltage being measured.

2. How does the resistance of a voltmeter affect the accuracy of measurements?

The higher the resistance of the voltmeter, the more accurate the measurement will be. This is because the voltmeter draws less current from the circuit, minimizing any impact on the voltage being measured.

3. Can the resistance of a voltmeter be adjusted?

No, the resistance of a voltmeter is fixed and cannot be adjusted. It is determined by the design and construction of the voltmeter.

4. How does the resistance of a voltmeter compare to that of an ammeter?

The resistance of a voltmeter is much higher than that of an ammeter. This is because an ammeter is designed to measure the current flowing through a circuit, so it needs to have a low resistance in order to not affect the current being measured.

5. Can multiple voltmeters be connected in series or parallel?

No, voltmeters should not be connected together in either series or parallel. This will alter the resistance of the voltmeters and affect the accuracy of the measurements.

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