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School project help - beginner!

whatishername8

New Member
Hi!

So we have this school project and they didn't quite explain how we're supposed to use all of the instruments. So for example, for the circuit in the picture we're supposed to check kirchoff's laws. I know that the ampermeter is connected in series and the voltmeter is connected in parallel.... I just don't quite see enought places in this model to connect them. For example if I need to check the first kirchoff law for let's say node number 1, i can see that for current 13 i can connect the ampermeter instead of the short circuit....for current 14 i can probably circumvent and touch one part to the resistor and connect the other one through the connector of the voltage source. But, current 12 is baffling me, i don't see where I'm supposed to put the connectors for the ampermeter. In the pictures I sent there is a scheme of the circuit, the irl model and how the resistors look irl. The connectors are what we call "banana connectors" and they have holes in them if we need to plug something in as a parallel circuit. The resistors plug inside of the circuit by using those probe-like legs that you can see in one of the pictures. Up top, I think there are also places where you can touch the resistors for measuring.

I'm sorry if this is confusing, they didn't explain anything and English isn't my primary language... I hope someone can help!

P.S. Sorry for the bad quality, i had to take screenshots off of online lectures.

Thank you in advance!

ploca.png
skica.jpg
 

JimB

Super Moderator
Most Helpful Member
ampermeter
A bit of terminology, in English, the correct word is "ammeter" not "ampermeter".

If you want to know the current in the resistor between point 1 and point 2, simply measure the voltage across the resistor, ie the voltage between points 1 and 2.
You know the value of the resistor, it is 100 Ohm.
So apply Ohms law and calculate the current.

I = V/R, so if V =7.5 volt then I = 7.5/100 = 0.075 Amp

JimB
 

whatishername8

New Member
A bit of terminology, in English, the correct word is "ammeter" not "ampermeter".

If you want to know the current in the resistor between point 1 and point 2, simply measure the voltage across the resistor, ie the voltage between points 1 and 2.
You know the value of the resistor, it is 100 Ohm.
So apply Ohms law and calculate the current.

I = V/R, so if V =7.5 volt then I = 7.5/100 = 0.075 Amp

JimB

Thank you so much for answering!
I thought I could just use Ohm's law to get the current, but I think that they want us to measure it somehow. On a different forum I got the proposition to basically pop the resistor out , connect the ammeter into the circuit and then touch the resistor like a jumpstart cable. I think this would solve the problem, but I'm not sure that's what they want us to do and I'm not sure whether it's safe.
 

JimB

Super Moderator
Most Helpful Member
On a different forum I got the proposition to basically pop the resistor out , connect the ammeter into the circuit and then touch the resistor like a jumpstart cable.
Yes, you can do that.

I'm not sure whether it's safe.
The circuit is powered by a simple 24v supply, I assume that this is a low current (one or two amps max) supply, so if all goes wrong you will not cause a rift in the space-time continuum !
I think that it will be safe enough.

JimB
 

wkrug

Active Member
There is no Point to insert an Ammeter between the Points 1...4 without affecting the whole circuit.
An Ammeter is ideally like a short circuit.
In Your schematic the upper Resistors would be set paralell to +24V via Ammeter and that will give You an other sum resistance then without that.

To prove Kichhoffs law You have to measure the current is series to any resistor in the star.
At point 2 the ingoing and outgoing currents had to be 0.
I agree in the actual circuit there is no point to insert an Ammeter there.
You only can measure the Voltage across the resistors and calculate the current then.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
My only guess is that your supposed to "solve" the circuit and verify your answer by actually measuring

You have those two 100 ohm resistors and two test points near each other, so you need to calculate that value and measure it.

Where there is a short, like the bottom line, I think the idea is to calculate a current and measure it. The problem with MOST ammeters is that it introduces a resistance, so unless you have a feedback ammeter or one with a very low series resistance, it seems pointless.
 

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