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QUESTION: 1

Foucault Currents are also called

Solution:

Eddy currents are the currents which are induced in a conductor whenever the amount of linked magnetic flux with the conductor changes. These were **discovered by Foucault in the year 1895 **and hence they are also called **Foucault currents.**

__Eddy currents:__

QUESTION: 2

Which of the following will not increase the size and effect of eddy current?

Solution:

Stronger magnetic field, **thicker material **and **low resistivity material will increase** the size and effect of eddy current whereas **thinner material will reduce** the effect of eddy currents.

QUESTION: 3

Why is the iron core of a transformer made laminated instead of being in one solid piece?

Solution:

- The iron core of a transformer is made of
**Laminated silicon steel**with special insulated coating to limit Eddy current loss. - Electrical steel, also called lamination steel is specialty steel tailored to produce certain magnetic properties, such as a small hysteresis area (small energy dissipation per cycle, or low core loss) and high permeability.

QUESTION: 4

Eddy currents have negative effects. Because they produce

Solution:

- When a conductive material is subjected to a time-varying magnetic flux, eddy currents are generated in the conductor.
- These eddy currents circulate inside the conductor generating a magnetic field of opposite polarity as the applied magnetic field. The interaction of the two magnetic fields causes a force that resists the change in magnetic flux.
- However, due to the internal resistance of the conductive material, the eddy currents will be dissipated into heat and the force will die out. As the eddy currents are dissipated, energy is removed from the system, thus producing a damping effect.

QUESTION: 5

The no-load current drawn by transformer is usually what percent of the full-load current ?

Solution:

The no load current is** about 2-5% of the full load current **and it accounts for the losses in a transformer. These no-load losses include **core(iron/fixed) losses**, which contains **eddy current losses** & **hysteresis losses** and the **copper(I ^{2}R) losses **due to the no Load current.

QUESTION: 6

A circular coil of area 200 cm^{2} and 25 turns rotates about its vertical diameter with an angular speed of 20 ms^{-1} in a uniform horizontal magnetic field of magnitude 0.05 T. The maximum voltage induced in the coil is:

Solution:

It is induced EMF of periodic EMI, So formula is:

**E= NBAw**

Here w is angular speed.

So, E = 25×0.05×200×20/10000 =0.5V

QUESTION: 7

In electromagnetic induction, line integral of induced field E around a close path is __________, induced electric field is ___________.

Solution:

In electromagnetic induction, line integral of induced field E around a close path is **non zero**, and induced electric field is **non conservative**.

QUESTION: 8

In the dead beat galvanometer, the coil is wound on a frame made of:

Solution:

Aluminum is used as a coil which is a good conductor.

__Dead beat galvanometer:__

QUESTION: 9

Eddy currents can be induced in

Solution:

Eddy currents are produced by varying magnetic field in **solid plates, blocks and wires**.

QUESTION: 10

Eddy currents do not cause:

Solution:

Eddy current when produced it causes damping heat loss energy loss but **it don't produce any type of sparking.**

### Eddy Currents

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### Eddy Currents (Part - 1)

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### Eddy Currents (Part - 2)

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### Transformers and effect of eddy currents - Electromagnetic Induction

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