Aplastic rod has been bent into a circle of radius r = 8.00 cm. it has a charge q1 = +2.70 pc uniformly distributed along one-quarter of its circumference and a charge q2 = −6q1 uniformly distributed along the rest of the circumference. take v = 0 at infinity. (a) what is the electric potential at the center c of the circle? v (b) what is the electric potential at point p, which is on the central axis of the circle at distance d = 6.71 cm from the center?

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?

The direction of the current in an alternating current circuit remains constant. is direct. changes repeatedly. changes randomly.

Current vs. forcewhat type of relationship does this graph show?