Lenz's law applies to:

Options

A. lenses
B. cinema slides
C. atoms
D. electromagnetic induction

Explanation

**Solution:**

Lenz's law is a fundamental principle in electromagnetism that describes the direction of induced electromotive force (emf) and current in a conductor when it is exposed to a changing magnetic field.

1. **Understanding Electromagnetic Induction:**
- When a conductor (like a coil of wire) is placed in a changing magnetic field, an emf is induced in the conductor. This phenomenon is known as electromagnetic induction.

2. **Direction of Induced Current:**
- According to Lenz's law, the direction of the induced current (or induced emf) is such that it opposes the change in magnetic flux that produced it. This means that if the magnetic field through the loop is increasing, the induced current will flow in a direction that creates a magnetic field opposing the increase. Conversely, if the magnetic field is decreasing, the induced current will flow in a direction that tries to maintain the magnetic field.

3. **Mathematical Representation:**
- Lenz's law can be mathematically represented as:
\[ \text{emf} = -\frac{d\Phi_B}{dt} \]
where \(\Phi_B\) is the magnetic flux through the conductor. The negative sign indicates that the induced emf (and hence the induced current) opposes the change in magnetic flux.

4. **Applications of Lenz's Law:**
- Lenz's law is applicable in various scenarios, such as:
- Induction cooktops, where the changing magnetic field induces currents in the cookware.
- Electric generators, where mechanical energy is converted into electrical energy.
- Magnetic braking systems in trains, where induced currents oppose the motion of the train.

**Conclusion:**
Lenz's law is fundamentally applicable to electromagnetic induction, specifically in determining the direction of induced emf and current in response to changing magnetic fields.

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