Induced EMF help?

Question

An automobile has a vertical radio antenna 1.20 m long. The automobile travels at 78.0 km/h on a horizontal road where the Earth's magnetic field is 50.0 µT directed toward the north and downward at an angle of 65.0° below the horizontal.

(a) Specify the direction that the automobile should move to generate the maximum motional emf in the antenna, with the top of the antenna positive relative to the bottom.

south

north

west

-east

(b) Calculate the magnitude of this induced emf (epsilon).

___V

Answer 1

♠ coordinate system: the car should be traveling due East – this is +x direction;

as for magnetic field it has two components:

By=50μT*cos65° directed to the North – this is +y direction, and

Bz – we spit on it as it’s parallel to antenna;

♣ E=By*L*v = 50e-6*cos65* 1.2 *(78*1000/3600) =0.5e-3V; this is magnitude!

According to s***w rule E is directed from bottom end to the top! (+z direction);