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प्रश्न
State three factors which govern the speed of rotation of an electric motor.
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उत्तर
(i) The strength of current in the coil,
(ii) The number of turns in the coil,
(iii) The strength of the magnetic field.
संबंधित प्रश्न
Tick the most appropriate answer.
Which of the following methods is used to magnetize a magnetic without touching it by a magnet?
Show with the aid of a diagram how a wire is wound on a U-shaped piece of soft iron in order to make it an electromagnet. Complete the circuit diagram and label the poles of the electromagnet.
principle of an electric motor ?
State two factors on which the strength of induced e. m.f. depends.
Describe a simple Experiment to demonstrate that there Exists a magnetic field around a current-carrying conductor.
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.
What is a permanent magnet? Give one use of it.
The primary windings of a step-up transformer are usually made of thicker wire than the secondary. Explain.
(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.
