xercises 1. Two long bar magnets lying on a table with their south magnetic field of 0.6 T. What is the magnitude of the poles facing one another exert a force of 10 N on each magnetic force on this segment of wire? other. If the distance between these two poles is doubled, what is the new value of this force? E8. The magnetic force on a 30-cm straight segment of wire carrying a current of 5 A is 6 N. What is the magnitude 2. Two long parallel wires, each carrying a current of 4 A, of the component of magnetic field perpendicular to lie a distance of 10 cm from each other. What is the mag- the wire? netic force per unit length exerted by one wire on the E9. A coil of wire with 80 turns has a cross-sectional area other? of 0.04 m2. A magnetic field of 0.6 T passes through the 3. If the distance between the two wires in exercise 2 is coil. What is the total magnetic flux passing through tripled, how does the force per unit length change? the coil? Two parallel wires, each carrying a current of 2 A, exert a E10. A loop of wire enclosing an area of 0.03 m2 has a magnetic force per unit length on each other of 1.6 x 10-5 N/m. field passing through its plane at an angle to the plane. The What is the distance between the wires? component of the field perpendicular to the plane is 0.4 T, and the component parallel to the plane is 0.6 T. What is 5 A wire carries a current of 4 A. How much charge flows the magnetic flux through this coil? past a point on the wire in a time of 5 s? Ell. The magnetic flux through a coil of wire changes from A particle with a charge of 0.06 C is moving at right angles 6 Tom? to zero in a time of 0.25 s. What is the magnitude of to a uniform magnetic field with a strength of 0.5 T. The the average voltage induced in the coil during this change? velocity of the charge is 600 m/s. What is the magnitude of the magnetic force exerted on the particle? E12. A coil of wire with 60 turns and a cross-sectional area of 0.02 m' lies with its plane perpendicular to a magnetic Astraight segment of wire has a length of 10 cm and car- field of magnitude 1.5 T. The coil is rapidly removed from ries a current of 5 A. It is oriented at right angles to a the magnetic field in a time of 0.2 s.302 Chapter 14 Magnets and Electromagnetism a. What is the initial magnetic flux through the coil? E15. A step-down transformer is to be used to convert b. What is the average value of the voltage induced in voltage of 120 V to 6 V to power an electric train. ] the coil? are 300 turns in the primary coil, how many turns E13. A transformer has 15 turns of wire in its primary coil and there be in the secondary coil? 60 turns on its secondary coil. E16. A step-up transformer is designed to produce 1380 ' a. Is this a step-up or step-down transformer? a 115-V ac source. If there are 400 turns on the sec b. If an alternating voltage with an effective voltage of coil, how many turns should be wound on the primar 110 V is applied to the primary, what is the effective voltage induced in the secondary? E14. If 6 A of current are supplied to the primary coil of the transformer in exercise 13, what is the effective current in the secondary coil