# questions in physics help me

• Nov 26th 2010, 01:47 AM
r-soy
questions in physics help me
1 ) How is the potential difference across a resistor measured ?
2) What are resistances of ideal voltmeter and Ammeter ?
3)what is the advantage of difital Multometer to use as voltmeter ?

1) measured in peralled .
2 ) The internal resistance of an ideal voltmeter is infinity ohms. The internal resistance of an ideal ammeter is zero ohms.

3 )The digital readout gives you a single number instead of a dial pointing to several numbers on multiple scales

• Nov 26th 2010, 04:27 AM
Unknown008
1) Um... what do you mean by "measured in peralled"?

2) Right.

3) Um... you weren't given any information about the display of the voltmeter right? So, you don't know if it's a digital or if it's an analogue voltmeter... look for another advantage. Have you ever used a multimeter?
• Nov 26th 2010, 05:21 AM
r-soy
1 - I mean measured in parallel resistors

3 - A digital multimeter has the advantages of idiot-proofing and accuracy. The digital also has a built-in overload protection that many analog meters don't have, protecting the meter itself
• Nov 26th 2010, 05:33 AM
Unknown008
"I mean measured in parallel resistors"

This still doesn't make much sense to me...

You should probably put "By connecting a voltmeter across the resistor in parallel"
• Nov 26th 2010, 07:03 AM
r-soy
ok about number 1 i write By connecting a voltmeter across the resistor in parallel"

and what about Q3 is >> A digital multimeter has the advantages of idiot-proofing and accuracy. The digital also has a built-in overload protection that many analog meters don't have, protecting the meter itself (corect )
• Nov 26th 2010, 07:09 AM
Unknown008
Well, the most obvious advantage that I can think about when thinking about the Multimeter is its Multifunctions.

Multimeter - Wikipedia, the free encyclopedia

The basic ones can measure current, resistance and potential difference while the voltmeter can measure only potential difference.

Accuracy, yes for sure.

Idiot proofing... I don't know. Because one can get confused with all the options available on the multimeter.

I wouldn't say overload protection, because they too can get damaged by too large values of current, although the latest ones contain one or several fuses for protection of the apparatus.
• Nov 27th 2010, 09:11 PM
Roam
Quote:

Originally Posted by r-soy
2 ) The internal resistance of an ideal voltmeter is infinity ohms. The internal resistance of an ideal ammeter is zero ohms.,

Yes, an ideal voltmeter has infinite resistance so that no current exits in it.

Quote:

I mean measured in parallel resistors
The potential difference across a resistor can be measured with a voltmeter connected in parallel with the resistor.

And if you for example use galvanometer as a voltmeter, a resistor can be connected in series with the galvanometer.