Magnetic Fields and Magnetic Forces Concept Problems: 1. An insulating rod charged with positive charges is placed next to a compass as below. Does the compass needle rotate? a. Yes, clockwise. b. Yes, counterclockwise. C. No, not at all. Positively Pivot charged rod 2. A compass is placed next to a bar magnet. Which of the following shows the correct compass direction? N D. 3. A compass is placed above a wire (imagine the compass floating just above the page). With no current in the wire, the compass points north. Which direction will the compass point as the current increases? North B. D. 4. The following charged particles are moving along a circular path due to the force from an external magnetic field. Which of the charges are negative? D. 5. In which direction will the wire loop in the figure below experience a torque? a. Clockwise. b. Counterclockwise. C. It will not experience a torque.6. Draw the direction of the current which would produce the B fields shown below. a. b. O Written Problems: 7. For your senior project, you would like to build a cyclotron that will accelerate protons to 10% the speed of light. The largest vacuum chamber you can find is 50 cm in diameter. What is the minimum magnetic field strength you will need? 8. We have seen that the heart produces a magnetic field that can be used to diagnose problems with the heart. The magnetic field of the heart is a dipole field produces by a loop current in the outer layers of the heart. Suppose that the field at the center of the heart is 90 pT (that's 10"# T) and that the heart has a diameter of approximately 12 cm. Under this model, what current circulates around the heart to produce this field? 9. A biophysics experiment uses a very sensitive magnetic field probe to determine the current associated with a nerve impulse traveling along an axon. If the peak field strength 1.0 mm from an axon is 8.0 pT, what is the peak current carried by the axon? 10. A Boeing 747 aircraft with wingspan of 65 m is cruising at 260 m/s over northern Canada, where the magnetic field of the earth (magnitude 5.0 x 1075 T) is pointed straight down. What is the induced potential difference between the tips of the wings