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# Tag Archives: electromagnetic induction

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## The Ring Launcher Experiment and Eddy Currents

What are eddy currents?

The video focuses upon the demonstration of the concept of Eddy Currents and the application of Lenz Law, using a device called- RING LAUNCHER

Eddy currents are loops of electrical current induced within solid conductors by a changing magnetic field in the conductor according to Faraday’s law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.

Lenz’s law. A principle stating that an electric current, induced by a source such as a changing magnetic field, always creates a counterforce opposing the force inducing it. This law explains such phenomena as diamagnetism and the electrical properties of inductors.

Lenz’s Law explains the production of eddy current in a changing magnetic field.

Primarily, eddy currents will be introduced in the material, when an electrically conductive material is placed in the coils magnetic field an electromagnetic induction occurs.

The magnitude of the eddy currents produces a large current since the resistance of the metallic conductor becomes low. They may produce undesirable effects if the large eddy current is allowed to in the core of a choke coil, transformer, etc.

By making use of a laminated core, the eddy currents produced in the core of a transformer are reduced. In the present day, electric brakes are provided on the trains in addition to those vacuum brakes.

# CLASS XII – SAMPLE PAPER

## PHYSICS

Time allowed : 3 hours

Max. Marks : 70

General Instructions:

1. All questions are compulsory
2. There are 30 questions in total. Questions 1 to 8 carry one mark each, 9 to 18 carry two marks each, 19 to 27 carry 3 marks each and 28 to 30 carry 5 marks each.
3. There is no overall choice, but internal choices are provided. You have to attempt only one choice in full.
4. Use of calculator is not permitted.
5. You may use the logarithm table, if required.

1. Express dielectric constant in terms of capacitance.

2. What is magnetic susceptibility?

3. Define electromagnetic induction. (more…)

Class 12 students can download study materials in Physics here. The materials are prepared by experts in the field and can be used for first time study or  for a quick revision.

## Problem based on electromagnetic induction – motional emf

A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 m s–1, at right angles to the horizontal component of the earth’s magnetic field, 0.30 × 10–4 Wb m–2.
(a) What is the instantaneous value of the emf induced in the wire?
(b) What is the direction of the emf?
(c) Which end of the wire is at the higher electrical potential?

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## CHAPTERWISE REVISION QUESTIONS FOR CBSE CLASS XII

Electrostatics

ELECTROMAGNETIC INDUCTION AND ALTERNATING CURRENT

CURRENT ELECTRICITY

EM WAVES DUAL NATURE ATOMS AND NUCLEI

Ray Optics

wave optics

SEMICONDUCTOR DEVICES

communication system