Understanding Lenz's Law: A Guide for Simplification

In summary, Lenz's Law states that any induced current, voltage, or flux will always oppose the change causing it. This can be seen in practical examples such as a motor or generator, where the induced current works against the original current. This law is often demonstrated with a magnet and a coil of wire, where the induced current produces a magnetic field that opposes the original magnetic field.
  • #1
OJ-Hick
5
0
I am having great difficulty grasping the concept of Lenz's law. As far as I am unware it is derived as:

"any current driven by an induced e.m.f opposes the change causing it"

I do not really understand what this means - help would be greatly appreciated :)
 
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  • #2
The law of Lenz can be described as follows:

Induced quantities, such as current (mmf), voltage (emf), flux, & torque, are always oriented in a direction opposite to the original quantities.

A motor is started. It's current draw is large when at a standstill. Once the rotor spins, mmf/emf are induced into the stator. This induced current opposes the original current. Hence the net current draw decreases.

If I pedal a bicycle type generator under no load, and I control the speed to 300 rpm, for example. I then load the generator with 50 watts. The added load current has a magnetic field which produces a an additional torque. This torque counters my pedaling torque.

Otherwise, a motor or generator would create its own supply of energy. Induced quantities, electrical as well as mechanical, always act in the *opposite direction* to the corresponding original quantities.

Is this helpful?

Claude
 
  • #3
This Law is often demonstrated by moving a magnet towards the end of a long coil of wire. (Solenoid)
The result is that an emf is generated/induced in the coil.
If a current is able to flow in the coil, it flows in such a direction that the magnetic field it generates opposes the one that produced it- the one due to the magnet.
In practical terms, if you moved a N pole of a magnet towards the end of the coil, the current generated at the end of the coil would produce a N pole there - the N pole would be opposing the one producing it. (Like poles repel)
If you Google Lenz's Law demo you will find a better explanation of this than is possible in words, using some animations. There's also some stuff on YouTube.
 

1. What is Lenz's Law?

Lenz's Law is a fundamental law of electromagnetism that explains the direction of induced current in a conductor when it is exposed to a changing magnetic field. It states that the direction of the induced current will be such that it opposes the change in magnetic field that produced it.

2. What are the applications of Lenz's Law?

Lenz's Law has many practical applications, such as in the design of electric motors, generators, transformers, and inductive sensors. It is also used in electromagnetic braking systems, where the motion of a conductor through a magnetic field produces a current that opposes the motion, leading to deceleration.

3. How can Lenz's Law be simplified?

One way to simplify Lenz's Law is to use the concept of conservation of energy. Since the induced current always opposes the change in magnetic field, the work done by the induced current is equal to the work done by the changing magnetic field. This allows us to use energy considerations to determine the direction of the induced current without having to use the right-hand rule.

4. What is the relationship between Lenz's Law and Faraday's Law?

Lenz's Law and Faraday's Law are closely related and are often used together to understand electromagnetic induction. Faraday's Law states that the magnitude of the induced EMF is proportional to the rate of change of the magnetic flux, while Lenz's Law determines the direction of the induced current.

5. Can Lenz's Law be violated?

No, Lenz's Law is a fundamental law of electromagnetism and has been experimentally verified many times. It is based on the principles of conservation of energy and momentum and is considered to be a fundamental law of nature. Therefore, it cannot be violated.

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