Chapter 24, Problem 60A

To determine

The effect on the force on the wire when current changes direction in a earbud.

Explanation of Solution

Introduction:

When electric current flows through a wire, magnetic field is generated around the wire. The direction of the field is determined by the right hand rule. When this wire carrying current is placed under the influence of an external magnetic field it experiences a force in the direction which is determined by Fleming’s left-hand rule.

A conductor carrying current generates its own magnetic field. When placed in another magnetic field a force is exerted on the wire because of the interaction between the magnetic field and the field generated by the current carrying wire. The direction of the force is determined by Fleming’s left hand rule as shown below.

In an ear bud, the force on a coil caused by the magnetic field pushes the coil inwards and outwards depending on the current. Such motion causes the coil to vibrate which creates vibration in the air perceived as sound by the ear.

Conclusion:

In an ear bud the force on a coil caused by the magnetic field pushes the coil inwards and outwards depending on the current. Such motion causes the coil to vibrate which creates vibration in the air perceived as sound by the ear.