Lenz’s law

What is Lenz’s Law?

This law gives us the direction of induced emf. According to this law, the direction of induced emf in a circuit is such that it opposes the change in magnetic flux responsible for its production. Lenz’s law is in accordance with the principle of conservation of energy.

It states that the polarity of the induced emf and the direction of induced current is such that it opposes the very cause which produces it.

Consider the figure shown.

A rectangular loop ABCD is being pulled out of the magnetic field directed into the plane of the paper and perpendicular to the plane of the paper. As the loop is dragged out of the field the flux associated with the loop which is directed into the plane of the paper decreases.

The induced current will flow in the loop in the sense to oppose the decreasing of this flux. For this to happen magnetic field due to induced current in the loop must be directed into the plane of the paper. Hence the current in the loop must flow in the clockwise sense.

Fleming’s Right Hand Rule For Direction of Induced EMF

Fleming’s right hand rule also gives us the direction of induced emf or current, in a conductor moving in a magnetic field.

Stretch your right hand thumb, the index finger and middle finger such that all the three are mutually perpendicular to each other. If the thumb represents the direction of the motion of conductor, the index finger the direction of magnetic field, then the middle finger represents the direction of the current.

You may also want to check out these concept related to electromagnetic induction:

• Electromagnetic Induction
• Magnetic Flux
• Faraday’s Laws

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