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induced emf

A coil C having 120 turns of wire is wound on to one end of the core. The area of crosssection
of coil C is 1.5 cm2.
A Hall probe is close to the other end of the core.
When there is a constant current in solenoid S, the flux density in the core is 0.19 T. The
reading on the voltmeter connected to the Hall probe is 0.20 V.
The current in solenoid S is now reversed in a time of 0.13 s at a constant rate.
(i) Calculate the reading on the voltmeter connected to coil C during the time that the current
is changing.

The answer is 0.053 V but I got 0.026

I don't understand why the magnetic flux density must be multiplied by 2.
Original post by livesh
A coil C having 120 turns of wire is wound on to one end of the core. The area of cross-section of coil C is 1.5 cm^2.
A Hall probe is close to the other end of the core.
When there is a constant current in solenoid S, the flux density in the core is 0.19 T. The
reading on the voltmeter connected to the Hall probe is 0.20 V.
The current in solenoid S is now reversed in a time of 0.13 s at a constant rate.
(i) Calculate the reading on the voltmeter connected to coil C during the time that the current is changing.

The answer is 0.053 V but I got 0.026

I don't understand why the magnetic flux density must be multiplied by 2.


As the current is going from positive I0 to negative I0, the change in magnetic flux density is

ΔB = |(–0.19) – (0.19)|
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livesh
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6
Oh Thanks man

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