7. A single strand of wire of adjustable length is wound around the circumference of a round balloon that has a diameter of 18.0 cm. A uniform magnetic field with a magnitude of 2.40 T is perpendicular to the plane of the loop. If the balloon is blown up such that its diameter and the diameter of the wire loop increase to 28.0 cm in 0.030s, what is the magnitude of the average value of the emf induced in the loop? V

c. What is the resistance of the coil given that the diameter of the wire is 2.00 mm? (Recall, resistance of wire is given by R = ρL/A, where ρ is the resistivity of the metal, L is the length of the wire, and A is the cross-sectional area.)

4. A square circuit has 2 m sides and is perpendicular to a uniform magnetic field, with half the area of the loop in the field, as shown. The loop contains a 9 V voltage source. The magnitude of the magnetic field varies with time, with B = 6 + 5t, where B is the field strength in teslas and t is the time in seconds. (a) Determine the value of the induced emf in the circuit. (b) Which way does the overall current flow in the circuit, clockwise or counter-clockwise? Or is the current zero? Explain why your answer is correct.

2. An AC generator has 75 rectangular loops on its armature. Each loop is 14.0 cm long and 10.0 cm wide. The armature rotates at 1300 rpm about an axis parallel to the long side. If the loop rotates in a uniform magnetic field of 0.700 T, which is perpendicular to the axis of rotation, what will be the maximum output voltage of this generator? Volts