# Resonance of a driven pendulum

Objective

Demonstrate the resonance of a driven pendulum.

Procedure

Make a pendulum using two button magnets and a piece of paper. Suspend it and place the 3000T coil near that, as shown in figure.

- Connect the coil between SQ1 and ground

- Calculate the resonant frequency from the length of the pendulum

- Scan the frequency around the expected resonance frequency

Discussion

When SQ1 reaches the resonant frequency of the pendulum, the amplitude goes up due to resonance. A 4 cm (from the center of the magnet to the axis of oscillation) long pendulum resonated at around , almost tallying with its calculated natural frequency. The resonant frequency of the pendulum is given by , where is the distance from the center of the magnet to the point of suspension and is the acceleration due to gravity.

Repeat the experiment by changing the length of the pendulum.