which of ther following is constructed on the principle of electromagnetic induction?

Options

A. Galvanometer
B. Electric motor
C. Generator
D. Voltmeter

Answer

To determine which of the following devices is constructed on the principle of electromagnetic induction, we will analyze each option based on the principles of electromagnetic induction, specifically Faraday's Law and Lenz's Law.

### Step-by-Step Solution:

1. **Understanding Electromagnetic Induction**:
- Electromagnetic induction is the process where a changing magnetic field within a coil induces an electromotive force (EMF) in the coil. This is governed by Faraday's Law, which states that the induced EMF is proportional to the rate of change of magnetic flux through the coil.

2. **Identifying the Laws**:
- **Faraday's Law**: When a magnet moves towards or away from a coil, it induces an EMF in the coil.
- **Lenz's Law**: The direction of the induced current will be such that it opposes the change in magnetic flux that produced it.

3. **Analyzing Each Option**:
- **Galvanometer**: This device measures current and operates on magnetic torque, not converting mechanical energy into electrical energy. Thus, it does not work on the principle of electromagnetic induction.
- **Electric Motor**: An electric motor converts electrical energy into mechanical energy. This is the opposite of what electromagnetic induction describes, so it does not apply.
- **Generator**: A generator converts mechanical energy into electrical energy. It operates on the principle of electromagnetic induction, as it uses mechanical movement (like turning a magnet) to induce an EMF in a coil.
- **Voltmeter**: A voltmeter measures the voltage across components in a circuit. It does not convert energy types and does not operate on electromagnetic induction principles.

4. **Conclusion**:
- Among the options analyzed, the **generator** is the only device that works on the principle of electromagnetic induction, as it converts mechanical energy into electrical energy.

### Final Answer:
The device constructed on the principle of electromagnetic induction is the **generator**.