In which of the following devices, the eddy current effect is not used ?

Options

A. electric heater
B. induction furnace
C. magnetic braking in train
D. electromagnet

Explanation

To solve the question of which device does not utilize the eddy current effect, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Eddy Currents**:
Eddy currents are loops of electric current that are induced within conductors by a changing magnetic field due to Faraday's law of electromagnetic induction. They are produced when there is relative motion between a conductor and a magnetic field.

2. **Identify Applications of Eddy Currents**:
Eddy currents have specific applications, primarily:
- **Heat Dissipation**: Used in induction furnaces where high heat is required to melt metals.
- **Magnetic Braking**: Used in systems like trains where the motion is opposed by the induced currents to slow down the train.

3. **Analyze the Given Devices**:
We need to evaluate the devices mentioned in the question to see if they utilize eddy currents:
- **Induction Furnace**: Uses eddy currents for heating.
- **Magnetic Braking System**: Uses eddy currents to slow down moving parts.
- **Electric Heater**: Relies on Joule heating (resistive heating) and does not utilize eddy currents.

4. **Conclusion**:
Based on the analysis, the device that does not use the eddy current effect is the **Electric Heater**.

### Final Answer:
**Electric Heater** is the device in which the eddy current effect is not used.

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