INDUCTION PROBLEM 1 A rotating rectangular coil is 12 cm wide and 18 cm long, and is wound with 150 turns of wire with resistivity = 0.5 ohms/m. The coil spins at 30 revolutions/sec and B = 0.5T. The B field points INTO the surface. Find the peak induced EMF in the coil. Find the peak induced current. Sketch the current vs time graph.

INDUCTION PROBLEM 2 The solenoid shown produces a field of B = 0.005 IS, where IS is the solenoid current. A conducting ring with a diameter of 10 cm is placed over the end of the solenoid. (a) Find the induced voltage in the ring while the solenoid current is increasing at a rate of 5 amps per second. (b) Show the direction of the induced current in the drawing.

TRANSFORMER PROBLEM The primary coil of an ideal transformer is wrapped with 200 turns of wire and runs on 120V and 5 amps, AC. What is the output voltage and current of the secondary coil if it is wrapped with 300 turns of wire? (b) Find the power in and power out.

AC vs DC PROBLEM What types of electrical systems run on DC instead of AC power? Why do most electrical systems run on AC?

3. a net force and a net torque. A rectangular loop is placed in a uniform magnetic field with the plane of the loop perpendicular to the direction of the field. If a current is made to flow through the loop in the sense shown by the arrows, the field exerts on the loop: 1. a net force. 2. a net torque. 3. a net force and a net torque. 4. neither a net force nor a net torque. Answer: 4. According to the right-hand rule, all four sides of the loop are subject to forces that are directed outward, with the force on each side canceling that on the opposite side.

When the switch is closed, the potential difference across R is 1. VN2 / N1. 2. VN1 / N2. 3. V. 4. zero. 5. insufficient information Answer: 4. Because the input is connected to a constant voltage source no potential difference is induced in the secondary coil.

2. a nonzero current for a short instant. 3. a steady current. The primary coil of a transformer is connected to a battery, a resistor, and a switch. The secondary coil is connected to an ammeter. When the switch is thrown closed, the ammeter shows 1. zero current. 2. a nonzero current for a short instant. 3. a steady current. Answer: 2.When the switch is thrown closed, it momentarily produces a time-varying current in the primary coil of the transformer. The iron core then acts as an electromagnet and generates a transient current in the secondary coil via electromagnetic induction.

A long, straight wire carries a steady current I A long, straight wire carries a steady current I. A rectangular conducting loop lies in the same plane as the wire, with two sides parallel to the wire and two sides perpendicular. Suppose the loop is pushed toward the wire as shown. Given the direction of I, the induced current in the loop is 1. clockwise. 2. counterclockwise. 3. need more information Answer: 2. As the loop approaches the wire, the magnetic flux through the loop will increase. To counteract this increase in magnetic flux, a current will start flowing to create a counteracting magnetic flux through the loop. Because the magnetic field of the wire points into the page at the location of the loop, the counteracting magnetic field of the loop must point out of the page. This requires a counterclockwise current.