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The magnetic flux linked with a coil is Φ=5t²+2t+3, where t is in seconds and Φ is in webers. At time t=1 s, the value of the induced emf is _____ volt.

Asked in GUJCET 2009 · Flux change and induced EMF

• (1) 1.2
• (2) 6
• (3) 14
• (4) 12

Step-by-step solution

Why the other options are wrong

• (1) No single slip produces 1.2 V; it is a tenth of the right value. Sanity check: (dΦ)/(dt)=10t+2 is 12 at t=1 s.
• (2) No single slip produces 6 V; it is half the right value. Sanity check: (dΦ)/(dt)=10t+2 is 12 at t=1 s.
• (3) No single slip produces 14 V. Sanity check: the constant 3 has no rate of change, and 10t+2 at t=1 s is 12.

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