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प्रश्न
State two differences between an electromagnet and a permanent magnet.
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उत्तर
| Electromagnet | Permanent magnet |
| It is made up of soft iron | It is made up of steel. |
| The magnetic field strength can be changed. | The magnetic field strength cannot be changed. |
| The electromagnets of very strong field can be made. | The permanent magnets are not so strong. |
संबंधित प्रश्न
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 the two properties of the magnetic lines of force around a circular coil.
How does a magnetic field set up by a solenoid change when a soft iron core is inserted inside solenoid?
How does a magnetic field set up by a solenoid change when strength of current in the solenoid is decreased?
State two advantages of an electromagnet over a bar magnet.
State three factors which govern the speed of rotation of an electric motor.
State the factors that can increase the speed of rotation of the coil in a D.C. motor.
State the position of armature coil relative to the direction of magnetic field, in a D. C. motor when the deflecting couple acting an the coil is maximum.
State the factors, on which depends the magnitude of the force acting on current carrying conductor, when it is kept in a magnetic field perpendicular to it.
(i) A straight wire conductor passes vertically through a piece of cardboard sprinkled with iron filings. Copy the diagram and show the setting of iron filings when a current is passed through the wire in the upward direction and the cardboard is tapped gently. Draw arrows to represent the direction of the magnetic field lines.
(ii) Name the law which helped you to find the direction of the magnetic field lines.
