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Fundamentals of Physics Halliday & Resnic 98 2 0401 0409 . CH30Inductance 1, 5, 7, 11, 13, 15, 21, 29, 31, 34, 37, 39, 45, 47, 51, 57, 63, 65, 73, 75 Problem 30-1 In Fig. 30-37, the magnetic flux through the loop increases according to the relation 2 6 7 B t t = + , where B is in milliwebers and t is in seconds. (a) What is the magnitude of the emf induced in the loop when 2 t s = ? (b) Is the direction of the current through R to the right or left? 30-37 <>(a) The magnitude of the emf is = = + = + = + = d dt d dt t t t B 6 0 7 0 12 7 0 12 2 0 7 0 31 2 . . . . . c h bg mV. (b) Appealing to Lenzs law (especially Fig. 30-5(a)) we see that the current flow in the loop is clockwise. Thus, the current is to left through R . Problem 30-5 In Fig. 30-39, a 120-turn coil of radius 1.8 cm and resistance 5.3 is coaxial with a solenoid of 220 turns/cm and diameter 3.2 cm. The solenoid current drops from 1.5 A to zero in time interval 25 t ms = . What current is induced in the coil during t ? 30-39 <>The total induced emf is given by 1 13 Fundamentals of Physics Halliday & Resnic 98 2 ( 29 2 2 ( ) ( ) 1.5 A (120)(4 T m A)(22000/m) 0.016m 0.025 s 0.16V. B d dB d di di N NA NA ni N nA N n r dt dt dt dt dt = - = - = - = - = - = - =-7 10 Ohms law then yields | |/ 0.016 V /5.3 0.030 A i R = = = . Problem 30-7 In Fig. 30-40, a wire forms a closed circular loop, with radius 2 R m = and resistance 4 . The circle is centered on a long straight wire; at time t = , the current in the long straight wire is 5.0 A rightward. Thereafter, the current changes according to 2 2 5 (2 / ) i A A s t =- . (The straight wire is insulated; so there is no electrical contact between it and the wire of the loop.) What is the magnitude of the current induced in the loop at times t ?... View Full Document

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