12.A coil with five series connected turn rotates at a speed of 1200 rpm. That flux per pole is 3 x 10⁶ Maxwell’s; the number of poles is 6. what is the amplitude of the emf induced in the coil if the flux is sinusoidally distributed

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.

5. A circular coil with a radius of 5 cm is made up of 30 loops. Its orientation makes the magnetic field lines normal to the area of the coil. If the magnetic field is varied from 0.25 T to 0.45 T in 1 hour, what is the average induced EMF in the coil?

4. A closely wound rectangular coil of 100 turns has dimension of 12.0cm x 25.0cm. In time t=0.0800 s the plane of the coil is rotated from a position where it makes an angle of 45.0o with a magnetic field of 0.975 T to a position perpendicular to the field. What is the average emf induced in the coil?