A higher Q factor in a resonant circuit results in:

• A. Wider bandwidth and poorer selectivity
• B. Narrower bandwidth and sharper selectivity
• C. No change in bandwidth
• D. Higher output power

Answer: (B)

Higher Q factor tightens the resonant peak, meaning the circuit responds strongly over a smaller frequency range. In a resonant circuit, Q is f0 divided by Δf, the bandwidth. When Q increases, Δf must decrease for the same resonant frequency, producing a narrower bandwidth. That narrower band gives sharper selectivity because signals close to the resonance are passed much more selectively while nearby frequencies are attenuated more strongly. Power output isn’t set by Q alone; it depends on the source, the impedance matching, and losses. So a higher Q leads to narrower bandwidth and better selectivity, not wider bandwidth, no bandwidth change, or necessarily higher output power.