The drawing shows a thin, uniform rod that has a length of 0.50 m and a mass of 0.080 kg. This rod lies in the plane of the screen and is attached to the floor by a hinge at point P. A uniform magnetic field of 0.28 T is directed perpendicularly into the plane of the screen. There is a current I = 3.8 A in the rod, which does not rotate clockwise or counter-clockwise. Find the angle θ. (Hint: The magnetic force may be taken to act at the center of gravity.)

Consider a resistor with color code “orange blue brown gold” and a measured value of 370 ω. determine the following: nominal value, tolerance, % error, and the probability of another resistor from the same manufacturing batch having a value closer to nominal than this one. use matlab or excel to evaluate the erf function.

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?

Astone weighing 1.5 kilograms is resting on a rock at a height of 20 meters above the ground. the stone rolls down 10 meters and comes to rest on a patch of moss. the gravitational potential energy of the stone on the moss is joules.