# little question

Discussion in 'Homework Help' started by Musab, Sep 20, 2008.

1. ### Musab Thread Starter Member

Sep 20, 2008
25
0
in a simple resistors circuit, why the measured value is always slightly less than the calculated value ?

Apr 5, 2008
15,796
2,383
Hello,

When you measure inside a circuit, it can be that other components are parallel to the resistor so the value you measure is lower.

Greetings,
Bertus

3. ### hgmjr Moderator

Jan 28, 2005
9,030
214
The best way to measure the value of a resistor that is part of a circuit is to lift or otherwise disconnect the resistor at one end and then measure it.

hgmjr

4. ### Musab Thread Starter Member

Sep 20, 2008
25
0
but even if there are no other components. Just resistors in series or parallel, the value is still slightly less

5. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Often there is a sneak current path around the resistor being measured. By disconnecting one end you can insure that the only current path seen by the meter is through the resistor being measured.

hgmjr

Last edited: Sep 20, 2008

Apr 5, 2008
15,796
2,383
Hello,

Are you pressing with your fingers to hold the resistor to measure ?
This can also lead to a lower value.

Greetings,
Bertus

7. ### Musab Thread Starter Member

Sep 20, 2008
25
0
thx

@bertus why will that happen ?

8. ### scubasteve_911 Senior Member

Dec 27, 2007
1,202
1
resistance of your finger/body in parallel with the measured resistor

9. ### hgmjr Moderator

Jan 28, 2005
9,030
214
The phenomenon being referred to by scubasteve_911 becomes more pronounced as the value of the resistor being measured increases.

hgmjr

10. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
Perhaps the meter is inaccurate.

11. ### jtolcou New Member

Nov 1, 2008
3
0
The resisitor should have one leg removed from the circuit and use alligatoe clips when making measurements to eliminate your body's resitance.