Working out the shunt resistance for a galvanometer circuit

  • Thread starter Bolter
  • Start date
  • #1
211
24

Homework Statement:

Find shunt resistance

Relevant Equations:

Ohm's law
Here is the problem

Screenshot 2020-02-07 at 14.24.02.png

I have tried to draw the set up for both cases which the question had described above, and came to these 2 equations. But I can't see how it would help me to work out the resistance of the shunt?

IMG_3807.JPG


Any help would be really great! Thanks
 

Answers and Replies

  • #2
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
9,113
2,505
The shunt should be in parallel with the galvanometer, not in series. See here.
 
  • Like
Likes etotheipi
  • #3
211
24
The shunt should be in parallel with the galvanometer, not in series. See here.
Ok I have made the changes to set up 1 and get these equations now

IMG_3808.JPG
 
  • #4
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
9,113
2,505
How are ##I## and/or ##I_g## in part 1 related to ##I## in part 2?
 
  • #5
211
24
How are ##I## and/or ##I_g## in part 1 related to ##I## in part 2?
Sorry I believe the I value in part 1 to be different to the I value in part 2?

To go about this question, I know that the voltage of the cell stays fixed in both cases. So could I find an expression for V in both part 1 and 2. Then equate them and solve for R_sh (the shunt resistance). I don't think this would be right as I would have more than 1 unknown there
 
  • #6
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
9,113
2,505
Sorry I believe the I value in part 1 to be different to the I value in part 2?

To go about this question, I know that the voltage of the cell stays fixed in both cases. So could I find an expression for V in both part 1 and 2. Then equate them and solve for R_sh (the shunt resistance). I don't think this would be right as I would have more than 1 unknown there
It's not the voltages that you should set equal. Reread the sentence that starts with "When the shunt is removed ..."
 
  • #7
211
24
It's not the voltages that you should set equal. Reread the sentence that starts with "When the shunt is removed ..."
OK I have had the time to rethink about this problem again. And I have redrawn the circuits again. This time I made use of Kirchhoff's 2nd law to help me

IMG_3810.JPG


I got a shunt resistance of 20 ohms here?
 
  • #8
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
9,113
2,505
That's what I got.
 
  • Like
Likes Bolter

Related Threads on Working out the shunt resistance for a galvanometer circuit

Replies
6
Views
250
Replies
16
Views
200
Replies
5
Views
7K
Replies
7
Views
6K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
3
Views
1K
Replies
2
Views
1K
Replies
3
Views
1K
Replies
4
Views
1K
  • Last Post
Replies
1
Views
1K
Top