Suppose you install a compass on the center of a car's dashboard. (a) Assuming the dashboard is made mostly of plastic, compute an order-of-magnitude estimate for the magnetic field at this location produced by the current when you switch on the car's headlights. (Suppose you have two 104-W headlights running in series from a 12-V battery with all the current going through the switch 62 cm from the compass. Model the current as being from a long straight wire.)
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(b) How does this estimate compare with the Earth's magnetic field?