2. A balloon contains 6 m3 of helium at a pressure of 100 kPa. As the balloon rises through
the atmosphere, the pressure falls and the balloon expands. Assuming that the
temperature does not change, what is the volume of the balloon when the pressure has
fallen to
a. 50 kPa
b. 40kPa? [4]

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?

Atelevision set that has been running for a while heats up even the air around it. which two laws of thermodynamics could be used to analyze this scenario

An electric clothes dryer has a resistance of 8 ohms. it draws 30 a of current. what is the voltage, in volts, of the wall outlet that it is plugged into?