Radio waves travel through air at approximately the speed of light, c. imagine your local fm radio station broadcasts plane waves travelling in the negative x-direction with a frequency of f = 94.9 mhz. the waveform of the electric-field component is e(x, t) = e 0 sin(φ(x, where φ(0, 0) = 0 and the amplitude is e0 = 0.12 n/c. part (a) enter an expression for the function ? (x, t) in radians, in terms of the defined quantities, the position. x and the time, t ? (x, ) = grade summarv deductions 1096 potential 90% submissions attempts remaining: 3 (5% per attempt) detailed view 50% 50% submit i give up! hints: 1 % deduction per hint. hints remaining: feedback: 1% deduction per feedback. g! lus 50% part (b) calculate the value of the electric field, in newtons per coulomb, of the wave at the position x-3.9 m at the time t-0.011

Search coils and credit cards. one practical way to measure magnetic field strength uses a small, closely wound coil called a search coil. the coil is initially held with its plane perpendicular to a magnetic field. the coil is then either quickly rotated a quarter-turn about a diameter or quickly pulled out of the field. (a) derive the equation relating the total charge q that flows through a search coil to the magnetic-field magnitude b. the search coil has n turns, each with area a, and the flux through the coil is decreased from its initial maximum value to zero in a time ∆t. the resistance of the coil is r, and the total charge is q = i∆t, where i is the average current induced by the change in flux. (b) in a credit card reader, the magnetic strip on the back of a credit card is rapidly “swiped” past a coil within the reader. explain, using the same ideas that underlie the operation of a search coil, how the reader can decode the information stored in the pattern of magnetization on the strip. (c) is it necessary that the credit card be “swiped” through the reader at exactly the right speed? why or why not?

When a light bulb shines, it gives off light energy and energy. a. heat b. potential c. chemical d. electrical

Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value