Answer:
Emf will become 3 times
So option (a) will be correct answer
Explanation:
The expression for induced emf is [tex]e=NAB\omega[/tex], here N is number of turns A is area B is magnetic field and [tex]\omega[/tex] is angular frequency
From the relation we can say that induced emf is directly proportional to frequency
It is given that initially voltage is 80 volt and frequency is increases from 40 Hz to 120 Hz
From the relation we can write [tex]\frac{e_1}{e_2}=\frac{f_1}{f_2}[/tex]
[tex]\frac{80}{e_2}=\frac{40}{120}[/tex]
[tex]e_2=240volt[/tex]
So emf will become 3 times
So option (A) will be correct option
If the frequency of the magnetic field is changed from 40Hz to 120Hz, the emf voltage will increase 3 times.
The maximum emf induced in a coil is determined by applying Faradays law as shown below;
[tex]emf = \frac{d\phi }{dt}[/tex]
[tex]E = NAB \omega \sin(\theta)\\\\E_{max} = NAB \omega \\\\E_{max} = NAB 2\pi f \\\\\frac{E_{max}_1}{f_1 } = \frac{E_{max}_2}{f_2 } \\\\E_{max}_2 = \frac{f_2 \times E_{max}_1}{f_1} \\\\E_{max}_2 = \frac{120 E_1}{40} \\\\E_{max}_2 = 3\ E_{max}_1[/tex]
Thus, we can conclude that, if the frequency of the magnetic field is changed from 40Hz to 120Hz, the emf voltage will increase 3 times.
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