Correct Answer - Option 4 : Conservation of energy
CONCEPT:
Lenz's Law:
- According to this law, the emf will be induced in a coil due to a changing magnetic flux in such a way that it will oppose the cause which has produced it.
- This law states that the induced emf in a conductor due to a changing magnetic flux is such that the magnetic field created by the induced emf opposes the change in a magnetic field.
\(\Rightarrow emf=-N\left ( \frac{d\phi}{dt} \right )\)
where N = number of loops and dϕ = Change in magnetic flux
- The above equation is given by Faraday's law, but the negative sign is a result of Lenz's law.
EXPLANATION:
- If the magnet is given some initial velocity towards the coil and is released, it will slow down because the emf will be induced in a coil due to a changing magnetic flux in such a way that it will oppose the cause which has produced it. Here the induced emf will try to stop the magnet.
- It can be explained as the following:
- The current induced in the coil will produce heat.
- From the energy conservation, if heat is produced, there must be an equal decrease in some other form of energy. Here is the kinetic energy of the moving magnet.
- So we can say that Lenz's law is associated with the conservation of energy.
- Hence, option 4 is correct.
