Assertion (A): In imperfect capacitors, the current does not lead the applied ac voltage by 90°.

Reason (R): When subjected to ac fields, the dielectric constant can be expressed as ∈^'_r - j∈^"_r.

1. The detector reads zero when phases of input signal and reference signal are different.
2. The detector acts as a linear rectifier.
3. The detector can be used as vector voltmeter.

Assertion (A): Gate triggering is the most commonly used method for triggering of an SCR.

Reason (R): Even a small gate current is sufficient to turn on an SCR.

1. It increases sensitivity by providing amplification to RF signal
2. It eliminates image frequency interference
3. It increases selectivity
4. It reduces noise level