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A galvanometer can be converted to ammeter by connecting a low resistance, called shunt in parallel with it. If a galvanometer of resistance 45 Ω is shunted by a resistance of 5 Ω what fraction of main current passes through the Galvanometer? What is the current which flows through the shunt?
- A question from Potentiometer (asked in Board Exam) (askphysics.com)
- CBSE Class 12 Syllabus for 2013 Board Exam (physicsfans.com)
I am using 18 gauge nicrome wire having ohm of 17.3 , 220 volt. I want to use 10 gauge wire how to decide the length?
18 gauge corresponds to a diameter of 1.22 mm
Therefore radius r1= 1.22/2=0.61 mm=0.00061m
10 gauge means diameter is 3.25 mm
Radius r2 = 3.25/2=1.625mm=0.001625m
Sine the resistance needs to be the same, we can use the formula
As resistivity is same.
Substitute the values and you will get the answer.
“Is ohm’s law universally applicable?”
The Ohm’s law states that “The current through a conductor is directly proportional to the potential difference applied across its ends provided the physical conditions such as temperature remains the same”
From the statement it is implied that it is not a universal law, and is applicable to conductors. It is not valid for semiconductors and electronic devices.
The substances which obey Ohm’s law are said to be ohmic and those which do not obey Ohm’s law are “Non Ohmic“