A wire fence surrounds a paddock with an area of 12 km2 = 12 x 106 I112. The Earth's magnetic field in the region of the paddock is B = 58yT at an angle 60" to the vertical. The Earth's magnetic field is decreasing at a rate of 0.063% per year. (For this problem, we'll assume that the proportional change is uniform in space and constant in time, though this is a poor approximation for the real field.) Part 1) Which of the following statements about magnetic flux are true? Cl Magnetic flux can be thought of as the number of magnetic field lines cutting through a surface. Cl Magnetic flux is independent of the direction between the magnetic field and the surface. Cl Magnetic flux is the number of magnetic field lines per unit area passing through a surface. Cl Magnetic ux increases in proportion to the magnetic field strength. Part 2) What is the magnetic flux through the paddock due to the Earth's field, now? mock = E Wb Part 3) When motorists passing through have remembered to shut the gates, the wire fence may be considered as a singleloop electrical circuit. What is the magnitude of the emf induced in the circuit by the Earth's magnetic field? mEv