Experiment using a potentiometer

[Electron Spin]

This experiment was on the characteristic of a filament lamp, and the other one similar to this was the characteristic of a semiconducting diode.

Just one question, we are using an ammeter in both experiments, would a milli-Ammeter be better?

A milli--ammeter is going to be 1000 times more sensitive than a meter with a full deflection of 1 ampere ..
But that is is not relevant here..I'm sure hundreds of students have used this same stuff
many times...I think the instructor is just trying to make u guys realize that a current meter has a very low resistance and a voltmeter has a very high resistance as not to upset the over all accuracy of the readings through or across the load.

 

[Taniaz]

Ok thank you :) I'll try again tomorrow and see how I get on.

 

[Electron Spin]

.....redundant post

 

[Electron Spin]

Ok thank you :) I'll try again tomorrow and see how I get on.

I'll be standing by...Gud luck!

 

[Electron Spin]

......

 

[andrevdh]

A closeup photo of just the blue CE multimeter will help.
That way we can instruct you how to use it to measure the current.
Anyway you should connect it just like the analogue one like I showed you.
Its black wire should be in the COM socket and it should be switched for DC (milli) amps.

 

[Taniaz]

Hello, so for the part with the bulb I disconnected the analogue ammeter and voltmeter and replaced them with digital multimeter.

The multimeter measuring the current was connected in series and the one measuring the voltage was connected in parallel.

I then disconnected the connections to the bulb and just tried to measure the current through the multimeter which was acting as the voltmeter.
The leads to the multimeter acting as the ammeter were connected to the 10 A connection and the ground.
The leads to the multimeter acting as the voltmeter were connected to the VΩmA connection and the ground. (I don't have a picture to go with this at the moment).

When I'd connect both meters to the 10 A connection, I'd get a reading on the multimeter acting as an ammeter and when I'd connect the multimeter acting as a voltmeter to VΩmA, it would give me a voltage but the multimeter acting as the ammeter would stop working.

 

[andrevdh]

The voltmeter has a very large resistance, so when you insert it the current would go way down creating the impression that the ammeter stopped working, but in fact the reading is way smaller so that you need to wire and put it on a much smaller scale setting. It is in fact dangerous to insert just the ammeter since it is creating a short circuit so that a part of the pentiometer is bypassed and much more current is drawn from the power supply, although it seems that the power supply has a reset button which would pop if you draw to much current from it.

 

[Taniaz]

We tried setting it to mA and micro-amps as well but it still showed 0. Yes the power supply does have a reset button, it usually resets when the wiper is allowing maximum current to go through.

 

[andrevdh]

It is set for direct current and not alternating current - assuming you are operating DC?
What make/model is is?
Also in this photo of yours you have to swop the red and black wires plugged into the ammeter around.