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CBSE - X - Physics - Magnetic Effects of Electric Current


Asked by gpnkumar0 2nd October 2017, 11:24 AM
Answered by Expert


The magnet is moved towards the coil with a certain speed. Now, the speed is doubled.
According to the Faraday's law of electromagnetic induction, the magnitude of induced emf is directly proportional to the rate of change of magnetic flux.
When the speed doubles, the rate of change of magnetic field increases and hence the magnetic flux also increases. This increases the induced emf.
Hence, E increases. So, option C is correct.
As E increases, I = E/R also increases. So, option B is also correct.
For charge: I = dq/dt.
dq = Idt = (E/R)dt
Using Lenz's law, E = L|-dΦ|/dt
So, dq = L|-dΦ|/dt × dt/R = L|-dΦ|/R
Hence, Q is independent of time. So, Q remains the same. Option A is also correct.
Hence, the incorrect option of the four is D.
Answered by Expert 25th October 2017, 3:19 PM

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