You're an electrical engineer designing an alternator (the generator that charges a car's battery). Mechanical engineers specify a 10-cmcm-diameter rotating coil, and you determine that you can fit 250 turns in this coil. To charge a 12-VV battery, you need a peak output of 17 VV when the alternator is rotating at 1500 rpm. What do you specify for the alternator's magnetic field?

13.78 mT

Explanation:

The peak voltage ε = ωNAB where ω = angular speed of coil = 1500 rpm = 1500 × 2π/60 rad/s = 50π rad/s = 157.08 rad/s, N = number of turns of coil = 250, A = area of coil = πr² where r = radius of coil = 10 cm = 0.10 m,

A = π(0.1 m)² = 0.03142 m² and B = magnetic field strength

So,

B = ε/ωNA  

substituting the values of the variables into the equation given that ε = 17 V

So, B = ε/ωNA

B = 17 V/(157.08 rad/s × 250 turns × 0.03142 m²)

B = 17 V/(1233.8634 rad-turns-m²/s)

B = 0.01378 T

B = 13.78 mT

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justin can't pay the full balance:

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b.   he can ask for the grace period to be extended.   but that's no solution, the bank will almost certainly refuse anyway, and there are much better options.   he knew the rules of his credit card when he started using it.

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