Key relationship
θ∝I; S=IgG/(Irange−Ig); Rseries=Vrange/Ig−G.
Physics · Class 12
Galvanometer and meter conversion
A radial field makes coil torque proportional to current. Add a small parallel shunt for an ammeter or a large series resistor for a voltmeter. Values beyond 90° indicate overload in this ideal model.
Open the interactive experiment →Galvanometer and meter conversion
அம்மீட்டருக்கு சிறிய இணை மின்தடை தேவை. வோல்ட்மீட்டருக்கு பெரிய தொடர் மின்தடை தேவை.
Key notes, relationships and model limits
Remember
A radial field makes coil torque proportional to current. Add a small parallel shunt for an ammeter or a large series resistor for a voltmeter. Values beyond 90° indicate overload in this ideal model.
Common trap
An ammeter uses a low-resistance parallel shunt; a voltmeter uses a high-resistance series multiplier.
Model limits
Linear radial-field galvanometer with 90° full scale. Unclipped deflection beyond full scale is an overload indicator, not usable calibrated motion.
What you will learn
Use the controls and plotted relation to explain galvanometer and meter conversion.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
For G=100 Ω, Ig=1 mA and range 1 A, S≈0.1001 Ω; for 10 V, Rseries=9900 Ω.
Why this matters
The model connects galvanometer and meter conversion with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Converting a galvanometer to an ammeter requires?
- A high resistance in series.
- A low resistance shunt in parallel.
- A high resistance in parallel.
Read the explanation
A low resistance shunt in parallel.
Course connection: Class XII Chapter 4. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.