The emf induced across the wing-tips of a flying aircraft is of the order of several millivolts. Can this value be obtained using a sensitive millivoltmeter connected across the wing-tips? Explain your answer.

Not if connections are actually made to the wing tips. The wires to the terminals of the voltmeter will have the same emf induced, and this will cancel out the emf between the wing-tips.

I assume that the small emf is a result of the plane cutting across magnetic field lines of the earth.

If the wires leading to the ends of wing are NOT connected there I believe the EMF can be read. It will be induced in the lead wires of the voltmeter

In order to determine if a sensitive millivoltmeter connected across the wing-tips can measure the induced emf in a flying aircraft, we need to consider the factors involved.

Firstly, the emf induced across the wing-tips of a flying aircraft is of the order of several millivolts. This emf is a result of the aircraft cutting across the magnetic field lines of the Earth.

If we connect the wires from the millivoltmeter directly to the wing-tips, the wires will also experience the same induced emf. This means that the emf induced in the wires will cancel out the emf between the wing-tips, and the voltmeter will not be able to measure the induced emf accurately.

To overcome this issue, we need to ensure that the wires leading to the ends of the wing are not connected. By doing this, the emf will only be induced in the lead wires of the voltmeter, and not in the connecting wires between the wing-tips and the voltmeter. This will allow the millivoltmeter to accurately measure the induced emf across the wing-tips of the flying aircraft.

Therefore, if proper precautions are taken to avoid the cancelation of induced emf by not connecting the wires to the wing-tips directly, a sensitive millivoltmeter can be used to measure the induced emf.