Which of the following statements are correct about the errors in PMMC instruments?
I. The swamping resistance is included in series with the moving coil to reduce errors.
II. The swamping resistance is included in parallel with the moving coil to reduce errors.
III. Errors are caused by weakening of the permanent magnet due to aging.
IV. Errors are caused by weakening of the spring due to aging and temperature.
1
Only II, III and IV
2
Only I, III and IV
3
Only III and IV
4
Only I and III