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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
The diagram shows a coil wound around a U shape soft iron bar AB.
1) What is the polarity induced at the ends A and B when the switch is pressed?
2) Suggest one way to strengthen the magnetic field in the electromagnet
3) What will be the polarities at A & B if the direction of current is reversed in the circuit?
State two ways of magnetising an iron piece?
principle of an electric motor ?
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.
Answer the following in short.
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State the principle of a D. C. motor.
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