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प्रश्न
Under what conditions permanent electromagnet is obtained if a current carrying solenoid is used? Support your answer with the help of a labelled circuit diagram.
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उत्तर
The following conditions are required to obtain permanent electromagnet when a current-carrying solenoid is used :
- Rod inside the solenoid should be made of a magnetic material like steel which should retain magnetic properties for a long time after magnetization.
- The current through the solenoid should be direct current.
- The number of turns in the solenoid should be large and closely packed so that a strong uniform magnetic field inside it is produced.
APPEARS IN
संबंधित प्रश्न
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
The adjacent diagram shows a small magnet placed near a solenoid AB. Current is switched on in the solenoid by pressing the key K.
- State the polarity at the ends A and B.
- Will the magnet be attracted or repelled? Give a reason for your answer.
The following diagram shows a spiral coil wound on a hollow carboard tube AB. A magnetic compass is placed close to it. Current is switched on by closing the key.
- What will be the polarity at the ends A and B?
- How will the compass needle be affected? Give reason.
State two ways by which the magnetic field due to a current carrying solenoid can be made stronger.
Why does a current carrying freely suspended solenoid rest along a particular direction? State the direction in which it rests.
A current carrying solenoid behaves like a ______.
- What name is given to a cylindrical coil of diameter less than its length?
- If a piece of soft iron is placed inside the coil mentioned in part (a) and current is passed in the coil from a battery, what name is then given to the device so obtained?
- Give one use of the device mentioned in part (b).
Derive the expression for the heat produced due to a current ‘I’ flowing for a time interval ‘t’ through a resistor ‘R’ having a potential difference ‘V’ across its ends. With which name is the relation known? How much heat will an instrument of 12W produce in one minute if it is connected to a battery of 12V?
Draw magnetic field lines in and around a current-carrying straight solenoid.
The diagram shows a current-carrying coil passing through a cardboard sheet. Draw three magnetic lines of force on the board.
State two factors on which magnitude of magnetic field at the centre depends.
Sketch the lines of force of the magnetic field of a solenoid. How does its field compare with that of a bar magnet?
What is a solenoid? Why do we usually keep its diameter small in comparison to its length?
What does the divergence of magnetic field lines near the ends of a current carrying straight solenoid indicate?
The diagram below shows an insulated copper wire wound around a hollow cardboard cylindrical tube. Answer the questions that follow:
- What are the magnetic poles at A and B when the key K is closed?
- State two ways to increase the strength of the magnetic field in this coil without changing the coil.
- If we place a soft iron bar at the centre of the hollow cardboard and replace the DC source with an AC source then will it attract small iron pins toward itself when the current is flowing through the coil?
A circuit contains a battery, a variable resistor and a solenoid. The figure below shows the magnetic field pattern produced by the current in the solenoid.
- State how the magnetic field pattern indicates regions where the magnetic field is stronger.
- What happens to the magnetic field when the current in the circuit is reversed?
Observe the given figure of a current-carrying solenoid and write the labels of A and B correctly.
For the current carrying solenoid as shown, draw magnetic field lines and give reason to explain that out of the three points A, B and C, at which point the field strength is maximum and at which point it is minimum?
Refer to the image below and state how the magnetic field pattern indicates regions where the magnetic field is stronger outside the magnet. What happens to the magnetic field when the current in the circuit is reversed?
Differentiate between a circular coil and a solenoid.
