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प्रश्न
What is an electromagnet?
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उत्तर
An electromagnet is a temporary strong magnet made from a piece of soft iron when current flows in the coil wound around it. It is an artificial magnet.
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संबंधित प्रश्न
State two ways of magnetising an iron piece?
Suppose you are given a long bar magnet and you are asked to break it into four small magnets. Draw diagrams showing the polarities of each broken part.
Name two factors on which the strength of magnetic field of an electromagnet depends and state how does it depend on the factors stated by you.
State three uses of an electromagnet?
What is an electric motor?
principle of an electric motor ?
Name the type of transformer shown in fig . What changes will you observe regarding the brightness of the lamp, if
(a) The no. of turns in the secondary is doubled?
(b) The part X of the transformer is removed?
( c) The core of the transformer is made out of copper?
(d ) The A.C. supply is replaced by D.C.?
The magnetic flux through a coil having 100 turns decreases from 5 milli weber to zero in 5 second. Calculate the e.m.f. induced in the coil.
A straight wire is held vertical and current is passed in it in the upward direction. A compass needle is kept near the wire in north of it. How is the needle deflected? What is the change in the deflection of the needle if the current in wire is reversed?
Describe a simple Experiment to demonstrate that there Exists a magnetic field around a current-carrying conductor.
How does a magnetic field set up by a solenoid change when number of turns are increased?
Why is soft iron generally used as the core of the electromagnet?
State the condition when an electric charge can give rise to a magnetic field.
State two advantages of an electromagnet over a bar magnet.
State three factors which govern the speed of rotation of an electric motor.
What energy conversion takes place during the working of a d c motor?
What is dynomo (a.c. generator)? State the principle on which it works.
The primary windings of a step-up transformer are usually made of thicker wire than the secondary. Explain.
