What would be the ameter reading?

  • Thread starter AlokBehria
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In summary: It's too easy of a question to be worth all this time we're spending on it. -berkeman-I think that the switch is an old fashioned knife switch that just disconnects the voltmeter from the power supply. So, when you close the switch, the voltmeter will just read 0V. I don't think there is anything else going on here.Also, I don't know why they're asking you to calculate the value of the resistors if they are already telling you that the resistors are identical. That means that R1=R2=R3... and so on.
  • #1
AlokBehria
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Hi All,

I have attached a bmp file indicating the diagram. Now, in the diagram shown alongside the cell and the ammeter both have negligible resistence.The resisters are identical with switch K open. the ameter reads 0.6 A . what will be the ammeter reading when the switch is closed?

Few more questions...

Q1 . Two resistence when connected in parellal give resultent value of 2 ohm. calculate the value of each resistence .

Q2 A resister a resistence of 176 ohm. how many of these resisters should be connected in parellal so that their combination draws a current of 5 ampers from a 220 volt supply line.

hare krishna
Alok
 

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  • #2
Thread moved from General Physics to Homework Help, Intro Physics.

Welcome to the PF, AlokBehria. Homework and coursework questions should go here in the Homework Help forums, and not in the general technical forums. Also, we require that you show us the relevant equations and show us some of your own work, before we can begin to give you tutorial help and advice.

So, how would you approach these questions? Also, I think there is something wrong with the questions. When you close switch K, where will the smoke and fire be seen first?
 
  • #3
I will wait for the file to load, but for now I'll help you with your other 2 questions.

Q1.

The total resistance of parallel resistors is:

[tex]R_T = \frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n}[/tex]

A shortcut to finding the total resistance of 2 parallel resistors is:

[tex]R_T = \frac{R_1R_2}{R_1 + R_2}[/tex]

Q2.

Using the first equation above and Ohm's Law, you have:

[tex]V = I R_T[/tex]

[tex]V = I (\frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n})[/tex]

Now, you know your voltage and your current, so you can find [tex]R_T[/tex]. Once you have [tex]R_T[/tex] and you know what value the resistors need to be, you can find how many resistors you need.
 
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  • #4
Thanks for the help, but I am not able to solve the question as per your suggestion, so would you elaborate more on both the question?

hare krishna
Alok
 
  • #5
AlokBehria said:
Thanks for the help, but I am not able to solve the question as per your suggestion, so would you elaborate more on both the question?

hare krishna
Alok

Which question can't you solve? 1 or 2?
 
  • #6
Q2, please help me.
 
  • #7
EugP gave you all the help you need in post #3. Stop trying to have us solve the question for you -- that's not how the PF works. You are *required* to show us your own work in order for us to help you. Please show us some of your work on these questions.
 
  • #8
Alright this should be more than enough information to help you solve the problem.

Like I said before:

<< Sorry, I have to delete this as too complete of an answer. Wait for more work by the OP. -berkeman- >>
 
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  • #9
we used V=IR_t

[tex]220 =5 (\frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n})[/tex]

Now if we solve the equestion, we diden't find the answer.
 
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  • #10
Remember, that question says that all the resistors are equal and in parallel. What happens to the total resistance when you put two equal-value resistors in parallel? What about 3 in parallel? What about N in parallel?
 
  • #11
EugP said:
Alright this should be more than enough information to help you solve the problem.

Like I said before:

<< Sorry, I have to delete this as too complete of an answer. Wait for more work by the OP. -berkeman- >>

No you're right I got a little carried away. Won't happen again.

AlokBehria, why don't you post any work you've done so far, with as many descriptions as possible of your thought process, so we could GUIDE you to how to solve the problem.
 
  • #12
have you one through the Q2 ? If yes, then where wud you find individual [tex]R_1[/tex] , [tex]R_2[/tex] and Rn
 
  • #13
AlokBehria said:
have you one through the Q2 ? If yes, then where wud you find individual [tex]R_1[/tex] , [tex]R_2[/tex] and Rn

I'm sorry but I don't understand your question.
 
  • #14
I woluld again repeat my question.

A resister has a resistence of 176 ohm. how many of these resisters should be connected in parellal so that their combination draws a current of 5 ampers from a 220 volt supply line

One more request, if you can open up that attached file..

Now, the question is ..

In the diagram given in the file, the cell and the ammeter both have negilagable resistence . the resistors are identical with the switch K open,the ammeter reads 0.6 amp. what will be the ammeter reading when the switch is closed. The answer shows the current in ammeter is 0.9 amp.

hare krishna
Alok
 
  • #15
Post your work so we can see how far you've gotten.
 
  • #16
ammeter reading

when three resistors with identical length connected with switch k open,the ameter reads 0.6 amp. reading
what will be the ammeter reading while the switch is closed.
it is noted that the cell and the ammiter both have negligiable resistence
 
  • #17
EUGP, if you can direct me a link so that I can go through the manuals to solve my problem.

hare krishna
Alok
 
  • #18
AlokBehria said:
EUGP, if you can direct me a link so that I can go through the manuals to solve my problem.

hare krishna
Alok

What manuals? I don't understand what you want, I gave you all the information you need. I'm not going to give you the answer.
 
  • #19
When the switch is closed the resistance in the circuit becomes zero, that is the power supply is shorted out. So it is actually not possible to say what the reading will be - each power supply will respond differently by tying to send the maximum possible current throught the wire that is shorting it out.

As far as the parallel combination of similar resistors goes - note that their total resistance needs to be 220/5 ohm.

http://www.circuit-magic.com/series_parallel.htm

http://www.physics.uoguelph.ca/tutorials/ohm/index.html
 
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  • #20
andrevdh said:
When the switch is closed the resistance in the circuit becomes zero, that is the power supply is shorted out. So it is actually not possible to say what the reading will be - each power supply will respond differently by tying to send the maximum possible current throught the wire that is shorting it out.

That would be the smoke that I was alluding to :eek:
 

What is an ammeter reading?

An ammeter reading is a measurement of the electric current flowing through a circuit, typically measured in amps.

How is an ammeter reading measured?

An ammeter reading is measured by connecting the ammeter in series with the component or circuit being measured. This allows the ammeter to measure the current flowing through the circuit.

What is the unit of measurement for an ammeter reading?

The unit of measurement for an ammeter reading is amps (A).

Why is it important to measure an ammeter reading?

Measuring an ammeter reading is important for monitoring the flow of electric current in a circuit and ensuring that it is within safe operating limits. It also allows for troubleshooting and identifying any issues within the circuit.

What factors can affect an ammeter reading?

An ammeter reading can be affected by the resistance of the circuit, the accuracy of the ammeter, and any external magnetic fields that may influence the flow of current. It is important to consider these factors when interpreting an ammeter reading.

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