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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
A line charge λ per unit length is lodged uniformly onto the rim of a wheel of mass M and radius R. The wheel has light non-conducting spokes and is free to rotate without friction about its axis (Figure). A uniform magnetic field extends over a circular region within the rim. It is given by,
B = − B0 k (r ≤ a; a < R)
= 0 (otherwise)
What is the angular velocity of the wheel after the field is suddenly switched off?
State three ways in which the strength of an electromagnet can be increased.
The most suitable material for making the core of an electromagnet is:
(a) soft iron
(b) brass
(c) aluminium
(d) steel
The switches in figure (a) and (b) are closed at t = 0 and reopened after a long time at t = t0.
(a) The charge on C just after t = 0 is εC.
(b) The charge on C long after t = 0 is εC.
(c) The current in L just before t = t0 is ε/R.
(d) The current in L long after t = t0 is ε/R.
Draw and label the diagram of a simple D.C. motor.
(a) Explain the rotation of the coil, giving a reason for your answer.
(b) How can you reverse the direction of rotation of the armature?
(c) How can you increase the speed of rotation of the motor?
State the condition at which we say the two coils kept close to each other are perfectly coupled with each other.
Write Fleming’s right hand thumb rule with the help of diagram.
Write the two names in the following diagram.
Fleming’s right hand rule.
A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then ____________.
The instrument that use to defect electric current in the circuit is known as ____________.
