Can Induced EMF and Current Work Together?

Until the 19th century, the only known concept of magnetism was ferromagnetism. Additionally, the idea of magnetism revolved around the concept that certain materials would attract specific materials when brought in contact with magnets, commonly iron (ferrous). When studying the relatively new field of electric currents, it was discovered that moving currents induced magnetic fields.

Mechanism

When a copper wire is wound in multiple rounds in the shape of a spring, it is called a solenoid. When a current passes through, the moving current produces a magnetic field, known as magnetic flux. 

This very idea can be reversed by switching off the current flow and placing a bar magnet inside the hollow solenoid. If the bar magnet is moved in and out of the solenoid, a current is produced due to the changing magnetic field. This induced voltage is called electromagnetic induction, and the force produced by the electromagnetic induction is called electromotive force (EMF).

Magnetic flux is directly proportional to the amount of current passing through the solenoid. It is to be noted that the number of turns in the solenoid is directly proportional to the magnetic field’s strength i.e. the more the turns in the solenoid, the stronger the magnetic field. 

Discovery

Michael Faraday is credited for this discovery, while Maxwell derived the equations for the same in the 18th century. Based on his observations, Faraday put forward the famous law of electromagnetic induction: a voltage difference is found in a circuit where there is relative motion between a closed circuit and a magnetic field. It also stated that the magnitude of this voltage is proportional to the rate of change of the flux. This means that current is induced in a solenoid when there is a change in the motions of the bar magnet and solenoid, and the amount of current induced is equal to the rate of change in the motion of the bar magnet and solenoid.

The following inferences were made by Michael Faraday under these conditions:
A. A strong bar magnet NS is placed in a solenoid that is connected to a switch and galvanometer 

1. A strong bar magnet is placed in such a manner that its north pole points to the solenoid and is moved up and down.

• When there is the slightest relative motion between the solenoid and bar magnet, a current is produced and recorded in the galvanometer.
• The current is temporary. It lasts as long as there is motion between the bar magnet and solenoid. Once the motion has interfered, the flowing current also stops.
• The direction of the current changes when the bar magnet is brought closer and taken away from the solenoid.
• The deflection in the galvanometer is more when the relative motion of the bar magnet is more i.e. the more the motion of either the solenoid or bar magnet, the more the current produced.
• When the bar magnet is reversed i.e. the bar magnet faces the solenoid with its south pole, the same observations are derived, but the direction of the current changes.

The Direction of Current and Induced EMF

Faraday was intrigued by the direction of the induced current and EMF. He later concluded this by the relation of the motion of the bar magnet and the solenoid. However, it is more convenient to get the direction of the induced current by Lenz’s law: the direction of the induced current is opposite to the motion of the bar magnet. Thus, the direction of the induced current and EMF are opposite in nature. It can be concluded that the direction of the induced EMF and current are in opposite directions. 

Fleming’s left-hand thumb rule is used to identify the direction of the current or magnetic field. If the left hand is placed in such a way that the thumb, index finger, and ring finger are perpendicular to each other, then the thumb points in the direction of the solenoid, the index finger points towards the direction of the magnetic field, and the thumb points towards the direction in which current flows.

Magnetic Field Strength

As discussed above, the strength of the magnetic field depends on various factors, primarily on the number of turns in the solenoid. The more the turns in the solenoid, the more the current has to flow in it, and more current makes the magnetic field stronger. Moreover, the initial amount of the current made to pass through the solenoid also determines the strength of the magnetic field. However, it is to be noted that when the frequency of the magnet’s motion is increased, the current flowing also increases proportionately.

Relation Between Induced and EMF Current

Current cannot be produced without a changing magnetic field, and a magnetic field cannot be induced without a moving charge. Each component is dependent on the other for its sustenance i.e. the slightest change in one causes a change in another.

Due to the chemistry of the material used to make the wire that is wound to make the solenoid, the current-carrying capacity also differs slightly. This is because different materials have different melting points, boiling points, and heat bearing capacities. This, in turn, affects the strength of the magnetic field. The same can be said regarding the chemistry of the magnet material, as different elements have different electron spins and valences, which affect the magnetising capacity of the element.

Conclusion

This article explains induced EMF and current. A voltage difference is found in a circuit where there is relative motion between a closed circuit and a magnetic field. It also stated that the magnitude of this voltage is proportional to the rate of change of the flux. This means that current is induced in a solenoid when there is a change in the motions of the bar magnet and solenoid, and the amount of current induced is equal to the rate of change in the motion of the bar magnet and solenoid. Current cannot be produced without a changing magnetic field, and a magnetic field cannot be induced without a moving charge. Each component is dependent on the other for its sustenance i.e. the slightest change in one causes a change in another.