PHYS 222 EXAM 1 OPENSTAX - Q & A

PHYS 222 EXAM 1 OPENSTAX - Q & A If you place a compass in a magnetic field, in what direction would the north end of the compass needle point? In the positive direction of the field An iron ring is magnetized by placi ...

PHYS 222 EXAM 1 OPENSTAX - Q & A If you place a compass in a magnetic field, in what direction would the north end of the compass needle point? In the positive direction of the field An iron ring is magnetized by placing it near the north pole of a bar magnet. How would the magnetic field lines of the iron ring appear once it is magnetized? Vertical lines arrow in, perpendicular to the right What is the direction of the magnetic field at the poles of a bar magnet? It points inward at the South Pole and outward at the north pole. If you place a compass at the three points in the figure below, at which point will the needle experience the greatest torque? The density of the magnetic field is maximized at A, so the magnetic compass needle will experience the greatest torque at A. A long straight wire is placed on a table top and electric current flows through the wire from right to left. If you look at the wire end-on from the left end, does the magnetic field go clockwise or counterclockwise? By pointing your right-hand thumb in the direction of current, the right-hand fingers will curl counterclockwise, so the magnetic field will be in the counterclockwise direction. How does the curve of a charged particle show whether it is charged positive or negative? The positive and negative charges will curve in opposite directions that can be determined using the right-hand rule governing electromagnetic interactions. Two particles with the same mass are moving perpendicular to a magnetic field at the same speed. The radius of the circular path traveled by the first particle is half the radius of the path traveled by the second particle. How do the charges of the particles differ? The charge of the first is twice the charge of the second. An electric charge is moving through a magnetic field. How does the speed of the charge change if the force on it doubles? It increases by a factor of 2. A current-carrying wire is in a uniform magnetic field. Initially, the field is perpendicular to the direction of the current. The field then shifts so that it is directed to an angle 30∘ to the direction of the current. How does the force per unit length on the wire change? It decreases to half its original value. A wire loop in the shape of a circle spins in a uniform magnetic field. How does the torque on the loop change if the radius of the wire is doubled at the same time that the current flowing through the wire is doubled? It increases by a factor of 8. A simple motor consists of a wire loop that spins in a uniform magnetic field. As the the loop spins, the angle between its pivot axis and the force on the loop changes. At what angle does the torque on the loop change direction? 0∘ Two current-carrying wires are parallel to each other. The current in one is increased by a factor of 2, the current in the other is increased by a factor of 3, and the distance between the wires is decreased by a factor of 13. What is the change in the force between the wires? It increases by a factor of 18. What is the purpose of the magnetic field in a cathode ray tube? Change the direction of electrons' motion Suppose you connect a resistor with a resistance of 4ohms in parallel with a resistor of resistance 8ohms. How would the total resistance compare with the individual resistances? Total resistance would be less than 4ohm. Can an insulating material be used to charge a conductor? If so, how? If not, why not? Yes, a charged insulator can charge a conductor upon contact. How are the materials that can be made into permanent magnets different from those that cannot be made into magnets? The spin of their electrons can be easily aligned. When the north pole of a magnet is thrust into a coil, what is the direction of the magnetic field exerted by the coil on the magnet? in the direction opposite the magnet's motion Explain how magnetic flux can be zero when the magnetic field is not zero. If the angle between magnetic field and area vector is 90∘ then its product is also zero which means that there is zero flux. Given a bar magnet, how can you induce an electric current in a wire loop? An electric current is induced if a bar magnet is moved through the wire loop. What factors can cause an induced current in a wire loop through which a magnetic field passes? Induced current can be created by changing the strength of the magnetic field, changing the size of the wire loop, or changing the orientation of the wire loop.