Temporary and Permanent Magnets
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List the methods used for magnetisation
What is magnetic induction? Describe in detail how a steel needle can be magnetized by induction.
The magnet used in a magnetic compass is:
electromagnet
permanent magnet
temporary magnet
none of the above
For magnetizing a magnetic substance, the single-touch method is used.
- True
- False
………precedes attraction in magnetization.
Assertion(A): When an iron piece is magnetised, its length slightly increases.
Reason(R): The closed molecular chains break down and all molecules align themselves in the direction of external magnetic field.
A and R are true and R is the correct explanation of A.
A and R are true but R is not the correct explanation of A.
A is true but R is false.
Both A and R are false.
What role does the magnetic induction play in the attraction of a piece of a soft iron bar by a magnet?
……….precedes attraction in magnetisation.
- finished just after.
- not finished for a long time.
- finished after some time.
- not charged.
a. Made of soft iron.
b. Strength of magnetic field can be changed.
c. Strong magnetic field but can be easily demagnetized
d. Polarity can be reversed
- Permanent magnet
- Bar magnet
- Electro-magnet
- Horse-shoe magnet
a. It is made of steel
b. It has a strong magnetic field which can be altered
c. Polarity cannot be reversed
d. Used in electric meters, magnetic compasses etc
- a, c and d
- All of the above
- a, b and c
- b, c and d
- Electromagnetism
- Static magnetism
- Induced magnetism
- Permanent magnetism
- Hammering the magnet
- Putting it in the water
- Cooling it
- Putting it in contact with iron
- electricity
- heating
- pressing
- non-metal
Write two differences between a permanent magnet and a temporary magnet.
What are magnetic keepers?
- True
- False
- True
- False
permanent magnet? Write two characteristic properties of materials which are required to select them for making permanent magnets.
- magnetic induction
- magnetic conduction
- magnetic attraction
- none of the above
Temporary magnets are made of
- Soft iron
- Steel
- Stainless Steel
- Copper
- energy loss is minimum
- density of steel is more
- residual magnetism of steel is more
- due to external magnetic field the magnetism does not destroy easily
Temporary magnets are made of cobalt.
- True
- False
- Attracts all substances
- Attracts only magnetic substances
- Attracts non-magnetic substances and repels magnetic substances
- Attracts magnetic substances and repels all non-magnetic substances