5
Question
(a) What is an electromagnet? Describe the construction and working of an electromagnet with the help of a labelled diagram.
(b) Explain why, an electromagnet is called a temporary magnet.
(c) Explain why, the core of an electromagnet should be of soft iron and not of steel.
(d) State the factors on which the strength of an electromagnet depends. How does it depend on these factors?
(e) Write some of the important uses of electromagnets.
(b) Explain why, an electromagnet is called a temporary magnet.
(c) Explain why, the core of an electromagnet should be of soft iron and not of steel.
(d) State the factors on which the strength of an electromagnet depends. How does it depend on these factors?
(e) Write some of the important uses of electromagnets.
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Solution
(a) Electromagnet:
It is a magnet that works on the principle of magnetic effect of current.
A temporary magnet consisting of a long coil of insulated copper wire wrapped around a soft iron core is called an electromagnet.
Construction and working:
We take a rod NS of soft iron and wind coil C of insulated copper wire around it. When we connect the two ends of the copper coil to a battery, an electromagnet is formed. The iron rod inside the coil becomes a strong electromagnet on passing a current. The magnetic field produced by an electromagnet is very strong.
(b) An electromagnet is called a temporary magnet because its magnetism stays only for the duration of current passing through it. All the magnetism disappears as soon as the current is switched off.
(c) The core of an electromagnet must be of soft iron because soft iron loses all its magnetism when current in the coil is switched off.
But if steel is used, it does not lose all its magnetism when current is switched off. Contrarily, it becomes a permanent magnet.
Therefore, steel cannot be used for making the core of electromagnets.
(d) Strength of an electromagnet depends on following factors:
1. Number of turns in the coil:
By increasing the number of turns in the coil, the strength of electromagnet can be increased.
2. Current flowing through the coil:
By increasing the flow of current in the coil, the strength of electromagnet can be increased.
3. Length of air gaps between poles:
By reducing the length of air gaps between the poles, the strength of electromagnet can be increased.
(e) Uses of electromagnet:
1. Electromagnets are used by doctors in MRI scanners.
2. It is used for treating knee pain by using pulsing electromagnetic field (PEMF).
3. It is used in magnetic levitation trains.
It is a magnet that works on the principle of magnetic effect of current.
A temporary magnet consisting of a long coil of insulated copper wire wrapped around a soft iron core is called an electromagnet.
Construction and working:
We take a rod NS of soft iron and wind coil C of insulated copper wire around it. When we connect the two ends of the copper coil to a battery, an electromagnet is formed. The iron rod inside the coil becomes a strong electromagnet on passing a current. The magnetic field produced by an electromagnet is very strong.
(b) An electromagnet is called a temporary magnet because its magnetism stays only for the duration of current passing through it. All the magnetism disappears as soon as the current is switched off.
(c) The core of an electromagnet must be of soft iron because soft iron loses all its magnetism when current in the coil is switched off.
But if steel is used, it does not lose all its magnetism when current is switched off. Contrarily, it becomes a permanent magnet.
Therefore, steel cannot be used for making the core of electromagnets.
(d) Strength of an electromagnet depends on following factors:
1. Number of turns in the coil:
By increasing the number of turns in the coil, the strength of electromagnet can be increased.
2. Current flowing through the coil:
By increasing the flow of current in the coil, the strength of electromagnet can be increased.
3. Length of air gaps between poles:
By reducing the length of air gaps between the poles, the strength of electromagnet can be increased.
(e) Uses of electromagnet:
1. Electromagnets are used by doctors in MRI scanners.
2. It is used for treating knee pain by using pulsing electromagnetic field (PEMF).
3. It is used in magnetic levitation trains.
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