Ammeter and Voltmeter in Series

In summary, when a battery of 12V and negligible internal resistance is connected to a 6Ω resistor, an ideal ammeter, and an ideal voltmeter, the ammeter will read 0A and the voltmeter will read 12V. This is because the infinite resistance of the voltmeter stops any current from flowing, while the ammeter only measures current in series and there is no voltage drop across the 6Ω resistor. If all components were connected in parallel, it would result in an extremely high voltage and current, potentially causing damage to the ammeter. It is important to leave a multi-meter on a voltage setting after use to avoid any accidents.
  • #1
Devs

Homework Statement


Hi! A battery of emf 12 V and negligible internal resistance is connected to a resistor of constant resistance 6 Ω, an ideal ammeter and an ideal voltmeter. The voltmeter and ammeter are in series with the cell and the resistor. What is the reading on each?

Homework Equations

The Attempt at a Solution


I realize that an ammeter is always in series but a voltmeter is always in parallel.
 
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  • #2
Devs said:
I realize that an ammeter is always in series but a voltmeter is always in parallel.

Correct. A volt meter is normally connected in parallel... but not in this question. What effect would that have?
 
  • #3
CWatters said:
Correct. A volt meter is normally connected in parallel... but not in this question. What effect would that have?

I thought that the reading on the voltmeter would be 0 and the ammeter will have a reading of 2A. But that isn't correct
 
  • #4
No that's not correct. What are the properties of an _ideal_ voltmeter?
 
  • #5
CWatters said:
No that's not correct. What are the properties of an _ideal_ voltmeter?

An ideal voltmeter has infinite resistance while an ideal ammeter has zero resistance.
 
  • #6
So what happens if you put an infinite resistance in series with a 12V source and a 6R resistor?
 
  • #7
CWatters said:
So what happens if you put an infinite resistance in series with a 12V source and a 6R resistor?
I am not sure but it will have infinite voltage and 2A current?
 
  • #8
No. Revise how to add resistors that are in series. For example a 100R and a 200R in series is equivalent to a 300R.
 
  • #9
CWatters said:
No. Revise how to add resistors that are in series. For example a 100R and a 200R in series is equivalent to a 300R.

So we add resistance when in series which gives us 0A because anything over infinity will limit to 0. And the voltage will equal 12?
 
  • #10
Correct.

The infinite resistance of the ideal voltmeter stops any current flowing. So the ammeter reads 0A.
If no current is flowing there is no voltage drop across the 6R so the voltmeter "sees" the full 12V.

If you fancy an exercise... What would happen if the 12V battery, 6R, ammeter and voltmeter were all in parallel with each other rather than series? (Hint: Don't try it at home).
 
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  • #11
CWatters said:
Correct.

The infinite resistance of the ideal voltmeter stops any current flowing. So the ammeter reads 0A.
If no current is flowing there is no voltage drop across the 6R so the voltmeter "sees" the full 12V.

If you fancy an exercise... What would happen if the 12V battery, 6R, ammeter and voltmeter were all in parallel with each other rather than series? (Hint: Don't try it at home).
Thanks a lot!

Regarding the exercise...since they are all in parallel, an extremely high level of voltage will pass through the ammeter causing it to blow up.
 
  • #12
Devs said:
Regarding the exercise...since they are all in parallel, an extremely high level of voltage current will pass through the ammeter causing it to blow up.

Yes. This is one reason why it is good practice to leave a multi-meter on a voltage setting when you finish using it. It would be very easy to leave it set on Amps and then next time you pick it up and go to measure the voltage of a battery and...
 

Related to Ammeter and Voltmeter in Series

What is the purpose of connecting an ammeter and voltmeter in series?

Connecting an ammeter and voltmeter in series allows for the measurement of both current and voltage in a circuit at the same time. This can help determine the resistance and power dissipation in the circuit.

How do you connect an ammeter and voltmeter in series?

An ammeter is connected in series with a circuit, meaning it is placed in the path of the current. The voltmeter is connected in parallel with a circuit, meaning it is connected across the component being measured.

What are the risks of connecting an ammeter and voltmeter in series?

Connecting an ammeter and voltmeter in series can cause a potential safety hazard, as it may result in short circuiting the circuit. It is important to use the correct equipment and follow proper safety precautions when connecting these instruments.

Can an ammeter and voltmeter be connected in series with any type of circuit?

Yes, an ammeter and voltmeter can be connected in series with both AC and DC circuits. However, it is important to ensure that the range of the instruments is suitable for the circuit being measured.

What are some common uses for connecting an ammeter and voltmeter in series?

An ammeter and voltmeter in series can be used to measure the current and voltage in household circuits, automotive circuits, and electronic circuits. It is also commonly used in electrical testing and troubleshooting to determine the health of a circuit.

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