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Class 9
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Strength of Electromagnets
Strength of Electromagnets
Theory
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1)
What happens to the strength of electromagnet as the number of cells in the circuit increases?
Increases
Remains unaffected
Decreases
Decreases first and then increases
2)
What happens to the strength of electromagnet as the number of turns in the coil decreases?
Increases
Decreases first and then increases
Decreases
Remains unaffected
3)
Identify the feature that is not a characteristic of an electromagnet
it acts like a magnet
it is controlled by electricity
use of an iron core reduces its strength
it can be turned on or off as required
4)
How should you coil the adjacent turns of wire in an electromagnet?
They should be parallel to each other
The direction of coiling doesn’t matter
They must always touch each other
The wire should always be wound on some material
5)
Materials such as iron when used as a core helps in increasing the strength of electromagnet. This is because iron is an example of
diamagnetic material
ferromagnetic material
highly dense material
strong material
6)
Electromagnets are used in
loudspeakers
MRI machines
electric generators
all of the above
7)
Strength of an electromagnet does not depend on
material of the core
number of turns of coil
length of the wire between the battery and the point of coiling
strength of current
8)
It is advised not to switch on the current in electromagnet for long duration because
the south and north poles of magnets shifts
fuse may blow off
the electromagnets heat up very fast
it may loss its magnetism
9)
Electromagnets are
permanent magnets
traditional magnets
natural magnets
temporary magnet
10)
What will happen when you bring a compass near the coiled wire of electromagnet?
The compass needle will not show any deflection
The compass needle will show deflection when the switch is off
Cannot be predicted
The compass needle will show deflection when the switch is on