# Question dealing with electromagnetic induction

1. Mar 10, 2008

### DSUND34

Question:
An automobile has a vertical radio antenna 1.2m long. The automobile travels at 65.0 km/h on a horizontal road where the Earth's magnetic field is 50.0 mT directed toward the north and downward at an angle of 65.0 degrees below horizontal.

calculate the magnitude of the induced emf.

I know that when a conducting bar of length l moves through a magnetic field B with a velocity of v so that v is perpendicular to B the emf is induced in the bar (called a motional emf)

E = -Blv

I'm stumped because this law only applies when the velocity and the magnetic field are perpendicular, and in this problem they are not. If anyone can explain this that would be awesome.

2. Mar 10, 2008

### PaintballerCA

The equation you have is a simplified one in that it assumes that they are perpendicular. So, what do we know about things that are perpendicular? This equation implies that when they are perpendicular, the voltage is at its maximum. When thinking about perpendicular and maximum, what comes to mind?