An astronaut is connected to her spacecraft by a 25-m-long conducting wire tether cord as she and the spacecraft orbit earth in a circular path at a speed of 3.0 x 103 m/s. At one instant the voltage measured between the ends of the wire embedded in the cord is measured to be 0.50V. Assume (worst-case) that the tether cord is perpendicular to the vertical component of Earth’s magnetic field at that location which is the peak ∆V measurement. (a) What is the magnitude of the Earth’s B-field at that instant? (b) Does the measured voltage change as the system moves from one location to another, and why? (c) What could you do to mitigate the problem?

A bar slides to the right at a constant speed of 2.1 m/s on two frictionless rails. The resistance of resistor R is 5.2 Q, and a 2.5 T constant magnetic field is directed perpendicularly downward, into the page. Let e = 1.2 m. Bin x x app x x (a) Find the current passing through the resistor. A I = (b) The direction of magnetic force on the moving bar is O No magnetic force O Right O Left O Out of the page O Into the page 1 x x x X x x x x X X x x * * x x x * * x x x x x x xx X X x x

Sodium ions (Na+) move at 0.858 m/s through a bloodstream in the arm of a person standing near a large magnet. The magnetic field has a strength of 0.254 T and makes an angle of 57.0° with the motion of the sodium ions. The arm contains 115 cm³ of blood with a concentration of 4.00 x 1020 Na+ ions per cubic centimeter. If no other ions were present in the arm, what would be the magnetic force on the arm? N

In the figure, an electron with an initial kinetic energy of 3.80 keV enters region 1 at time t = 0. That region contains a uniform magnetic field directed into the page, with magnitude 0.0100 T. The electron goes through a half-circle and then exits region 1, headed toward region 2 across a gap of 30.0 cm. There is an electric potential difference AV = 2000 V across the gap, with a polarity such that the electron's speed increases uniformly as it traverses the gap. Region 2 contains a uniform magnetic field directed out of the page, with magnitude 0.0168 T. The electron goes through a half-circle and then leaves region 2. At what time t does it leave? Number i Units × B₁ Region 1 Region 2 OB₂