What is the impact of an open circuit on voltmeter readings?

In summary, when the switch is closed, the voltage sources are at the same potential. When the switch is open, the voltage sources are at different potentials.
  • #1
Biker
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Homework Statement


What is the reading on voltmeter 1 and 2 when K is open?

http://blob:http://imgur.com/2d84e21a-63e2-4021-b4d9-e37231816d38 [Broken]
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Homework Equations


There isn't any.

The Attempt at a Solution


Okay so I have two answers for ##V_1## and ##V_2##:
What I am thinking is that it depends on how I define that source. If they define "Ideal" as to as a capacitor that has a specific voltage and a huge charge which makes the capacitor doesn't change its voltage as the current starts.
If that is what they mean then I would suppose the answer would be 12,12

Is this right?
 
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  • #2
The question says "when the switch is open". I think you have misread it.
 
  • #3
tech99 said:
The question says "when the switch is open". I think you have misread it.
I didnt? What did I misread?
If the ideal voltage is like a capacitor then anything connected to any terminal must have the same voltage. However the terminals they don't have to have the same voltage they are not connected by anything. However in case of a real battery. terminals are connected. Everything must come to a halt. So the potential must be the same everywhere.
 
  • #4
It's okay to state at the outset the assumptions you wish (or need) to make in order to arrive at your answer. For example, do you wish to assume the voltmeters are ideal or not? Do you wish to assume the voltage source is ideal or not ideal.

Ultimately, it is up to you to choose, but it's generally advisable that you choose reasonably, choose what will make it most straightforward to answer definitively, and/or choose what it's likely your examiner expects you to assume. :smile:
 
  • #5
An ideal voltage source maintains a constant potential difference regardless of the amount of current it has to supply. That includes negative, positive, or zero current.

This problem is intended to get you to think about what effect., if any, resistors have on potential when the current through them is zero.

Do some investigative calculations: Choose a value for R (maybe 11 Ω so that when the switch is closed the total resistance including the battery's internal 1 Ω will be 12 Ω and the circuit current will be 1 amp). Replace the switch with another resistance, say R1. Write expressions for the voltages with R1 as a variable. How do the voltages vary as R1 → 0 (equivalent to switch closed)? How about as R1 → ∞ (equivalent to switch open)?
 
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  • #6
Biker said:
I didnt? What did I misread?
I don't know whether this applies to your musings or not, but I'll spell it out just in case. In electronics, when we say a switch is "open" this is saying the copper contacts in the switch are not touching and the switch is not allowing current to flow through the circuit. When the switch is "closed" then the copper contacts touch so the circuit is completed and current can freely flow through the switch.

(
Confusion occasionally arises because switch terminology seems to be opposite to that of a farmer's gate which when open allows animals to pass freely, and when the gate is closed it blocks their passage.)
 
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1. What is an open circuit?

An open circuit is a circuit that is incomplete or broken, meaning there is a break or gap in the path of the electrical current.

2. How does an open circuit affect the voltmeter reading?

An open circuit will cause the voltmeter to read a value of zero, as there is no complete path for the electrical current to flow through.

3. Can an open circuit damage a voltmeter?

No, an open circuit will not damage a voltmeter. However, it may give inaccurate readings or no reading at all.

4. How can I test for an open circuit using a voltmeter?

To test for an open circuit, set the voltmeter to measure voltage and touch the probes to each end of the circuit. If the voltmeter reads zero, then there is an open circuit present.

5. How can I fix an open circuit?

To fix an open circuit, you will need to identify where the break or gap is in the circuit and repair or replace the faulty component. This may require soldering, rewiring, or replacing a damaged part.

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