Read the given Assertion (A) and Reason (R) carefully and select the correct option.

(A): Weakening of springs in PMMC is due to aging and temperature.

(R): Permanent magnets used in PMMC instruments tend to lose their strength over time.

Permanent Magnet Moving Coil (PMMC)

Characteristics of the PMMC instrument

• PMMC is used to measure only DC or the average value of an electrical quantity. 
• The PMMC instrument has a linear or uniform scale, hence, the deflecting torque produced is directly proportional to the current.
• Either spring or gravity control can produce the controlling torque in PMMC instruments.
• For spring control: Tc ∝ θ, and for gravity control: Tc ∝ sin θ 
• The damping torque in the PMMC instrument is provided by eddy current damping.

Explanation

• Statement A is True. The spring in PMMC (Permanent Magnet Moving Coil) instruments can indeed weaken over time due to mechanical fatigue (aging) and thermal effects (temperature).
• Statement B is also True. Permanent magnets do lose their magnetic strength over time, especially under high temperatures or external magnetic fields.
• Hence, both A and R are true, but R is not the correct explanation of A.