Edexcel A Level (IAL) Physics-5.24 Resonance- Study Notes- New Syllabus

Resonance in Oscillating Systems

Resonance occurs when an oscillating system is driven by an external force at a frequency equal to its natural frequency, causing the system to oscillate with maximum amplitude.

 Forced Oscillations

Resonance occurs in systems undergoing forced oscillations, where:

• An external periodic force acts on the system.
• The driving force supplies energy continuously.
• The system oscillates at the frequency of the driving force.

 Meaning of Resonance

Resonance occurs when:

Driving frequency = natural frequency

• Energy transfer from the driving force to the system is maximum.
• The amplitude of oscillation becomes maximum.
• The system vibrates strongly.

 Resonance Curve

The effect of resonance is shown using an amplitude–frequency graph.

• Amplitude is plotted on the vertical axis.
• Driving frequency is plotted on the horizontal axis.
• A sharp peak occurs at the resonant frequency.

Key idea: The peak corresponds to resonance.

Effect of Damping

Damping is the loss of energy from the system due to friction or air resistance.

• Increased damping reduces the maximum amplitude.
• The resonance peak becomes broader and lower.
• Resonant frequency shifts slightly to a lower value.

Light damping: sharp resonance peak Heavy damping: reduced resonance effect

Examples of Resonance

• A child on a swing being pushed at the right frequency.
• Musical instruments producing loud sounds.
• Radio tuning circuits.
• Bridges oscillating due to wind or traffic.

 Advantages and Dangers of Resonance

Useful applications:

• Musical instruments amplify sound.
• Radios select specific frequencies.
• Ultrasound and medical imaging.

Potential dangers:

• Structural damage to bridges and buildings.
• Machines vibrating excessively.
• Failure of mechanical components.