I had 2 questions:(adsbygoogle = window.adsbygoogle || []).push({});

1. My textbook derives that the equation from lenz's and faraday's law

emf = - d(N*flux)/dt

= B * dA/dT

where dA/dt = length * speed

However, why does the N value disappear in the new equation?

Also, this question is given after:

2. A metal propeller rotates in a verical plane with angular vel 85 rad per sec. The length of the propeller from tip to tip is 2.5m. Calculate emf generated between centre and tip of properller. The horizontal component of Earth's magnetic field is 22 x 10^(-6) T (micro Tesla)

The answer is 1.5 x 10^(-3) V. I dont get this.

I did emf = B * dA/dt

dA/dt = length * speed

= 1.25 * (1.25 * 85)

which gives emf = 2.9 x 10 ^ (-3) V

i.e. double the answer

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# Homework Help: Calculating emf from angular velocity

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