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VICPhysicsQuick questions

Unit 3: How do fields explain motion and electricity?

Quick questions on Electromagnetic induction: flux, Faraday and Lenz: VCE Physics Unit 3

8short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is magnetic flux?
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Magnetic flux through a flat loop of area AA in a uniform field BB is:
What is faraday's law (induced EMF)?
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When the magnetic flux through a coil changes, an EMF is induced. For a coil of NN turns:
What is bar magnet entering a coil?
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As the north pole approaches, flux into the coil increases; the induced current creates a field opposing the magnet (the near face of the coil becomes a north pole), repelling it.
What is bar magnet leaving a coil?
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Flux decreases; the induced current reverses to maintain the original flux (the near face of the coil becomes a south pole), attracting the receding magnet.
What is coil rotating in a uniform field?
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ΦB=BAcos⁡(ωt)\Phi_B = BA \cos(\omega t). The EMF is ε=NBAωsin⁡(ωt)\varepsilon = NBA\omega \sin(\omega t), a sinusoidal AC waveform.
What is q1?
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State Faraday's law and Lenz's law in words. [2 marks]
What is q2?
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A circular coil of 100100 turns and area 0.020.02 m2^2 is rotated from parallel to perpendicular to a 0.50.5 T field in 0.100.10 s. Calculate the average induced EMF. [3 marks]
What is q3?
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Refer to the Hornsdale wind-turbine generator. (a) State the source of the rotor field. (b) Calculate peak EMF for N=200N = 200, A=0.05A = 0.05 m2^2, B=1.2B = 1.2 T at 2525 Hz. (c) Apply Lenz's law to explain the reaction torque on the rotor.

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