Define quality factor of resonance in series LCR circuit.What is its SI unit ?

Explanation

### Step-by-Step Solution:

1. **Definition of Quality Factor (Q)**:
The quality factor (Q) of resonance in a series LCR (Inductor-Capacitor-Resistor) circuit is a dimensionless parameter that measures the sharpness of the resonance peak. It indicates how underdamped the circuit is and relates the maximum energy stored in the circuit to the energy dissipated per cycle.

2. **Mathematical Expression**:
The quality factor can be mathematically expressed as:
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