Emf induced in the windings of coil

AI Thread Summary
The discussion focuses on calculating the induced electromotive force (emf) in a tightly wound circular coil with 36.8 turns and a radius of 0.1m, as the magnetic field increases from 0 to 0.42T over 0.251 seconds. The user calculated the rate of change of the magnetic field (dB/dt) as 1.6733 T/s and used the formula for emf, resulting in a value of -1.934V. Feedback indicates that the negative sign is unnecessary since only the magnitude is required, and there may be issues with significant figures in the final answer. The user is encouraged to revise their answer based on these points. Accurate calculation and attention to format are essential for correct results.
dmckeog
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Homework Statement


a tightly wound circular coil has 36.8 turns, each of radius .1m. the uniform magnetic field is in a direction perpendicular to the plane of the coil. the field increased linearly from 0 to .42t in a time of .251s.
what is the emf induced in the windings of the coil?


Homework Equations


emf=-N(dmagflux/dt)
dmagflux=dBA/dt
emf=-n*A*dB/dt
A=pi*r^2

The Attempt at a Solution



dB/dt is rate I determined to be .42t/.251s=1.6733tpersec

emf=-36.8*pi*.1m*.1m*1.6733t per sec=-1.934v

 
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i really don't know what i have done wrong but the answer is wrong please help
 
Your thinking and method are correct. A couple of reasons why your answer might be rejected:
  • They are just looking for the magnitude of the EMF, so no "-" sign is needed
  • Wrong number of significant figures in the answer.
 
thanks a lot
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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