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प्रश्न
Why soft iron is preferred to be used as the core of the electromagnet of an electric bell?
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उत्तर
Soft iron is chosen to make the core of the electromagnet of an electric bell on account of the following two reasons:
(i) On account of high magnetic permeability of soft iron, it can be easily magnetized and demagnetized. So it makes a strong magnet when current flows through the solenoid but it is almost demagnetized when no current flows through the solenoid. This fact helps in the working of the electric bell.
(ii) The soft iron intensifies the magnetic field of the solenoid and so it helps in making a strong magnet.
संबंधित प्रश्न
Prove theoretically (electromagnetic induction) `e = (dphi)/(dt)`
Explain why, an electromagnet is called a temporary magnet.
In which of the following case does the electromagnetic induction occur?
The current is stopped in a wire held near a loop of wire .
The diagram 10 shows two coils X and Y. The coil X is connected to a battery S and a key K. The coil Y is connected to a galvanometer G.
When the key K is closed. State the polarity
(i)At the end of the coil X,
(ii)At the end C of the coil Y,
(iii)At the end C of the coil Y if the coil Y is (a) Moved towards the coil X, (b) Moved away from the coil X.
Fig. shows a simple form of an A.C. generator.
(a) Name the parts labeled A and B.
(b) What would be the effect of doubling the number of turns on the coil if the speed of rotation remains unchanged?
(c) Which of the output terminals is positive if the coil is rotating in the
direction shown in the diagram (anticlockwise)?
( d ) What is the position of the rotating coil when p.d. across its ends is zero? Explain why p.d. is zero when the coil is at this position .
(e) Sketch a graph showing how the p.d. across the ends of the rotating coil varies with time for an A.C. dynamo.
( f) On th e same sheet of paper and vertically below the first graph using the same time scale, sketch graphs to show the effect of
(i) Doubling the speed of rotation and at the same time keeping
the field and the number of turns constant,
(ii ) Doubling the number of turns on the coil and at the same time
doubling the speed of rotation of the coil, keeping th e speed
constant.
State Fleming’s Right Hand Rule.
Answer the following:
State the principles of the electric motor and electric generator.
Obtain an expression for motional emf from Lorentz force.
A current I = 10 sin(100π t) A is passed in first coil, which induces a maximum e.m.f of 5π volt in second coil. The mutual inductance between the coils is ______.
