Chapter 19 Magnetism CHAPTER 19 Conceptual Questions C1 A square coil and a triangular coil each have sides of length L The triangular coil has twice as many turns as the square coil If a the same current is sent through each coil when the coils are placed in the same uniform magnetic field making an angle of 30 with the planes of the coils which coil experiences the greater torque a the square coil b the triangular coil c Both coils experience the same torque d It depends on the magnitude of the magnetic field that the coils are placed in C2 Two parallel wires carry the a current I in the same direction Midway between these wires is a third wire also parallel to the other two which carries a current 0 5 I but in the direction opposite from the first two wires In which direction are the net forces on the outer wires a Since the net forces are zero there is no direction b Both forces are toward the center wire c Both forces are away from the center wire d Both forces on the two wires are in the same direction in space C3 Square coil A has 2N turns and sides of length L and square coil B has N turns and sides of length 2L When a current of 2 amps is sent through coil A and a current of 1 amp is sent through coil B which coil has the greater magnetic moment a coil A b coil B c Both have the same magnetic moment d More information is needed C4 Solenoid 1 has a length L cross sectional area A and N turns Solenoid 2 has a length 2L cross sectional area 2A and 2N turns Which solenoid has the greater magnetic field at its center when equal currents are going through them a 1 b 2 c Both have the same magnetic field d Since it depends on the values of A and L none of the above are correct C5 A beam of electrons is sent in the positive x direction in a region with a uniform magnetic field B in the positive y direction and a uniform electric field E in the positive z direction At which of the following speeds would the electrons be deflected in the positive z direction 68 Chapter 19 Magnetism a v E B b v E B c v E B d There is no speed for which this will happen 19 1 Magnets 1 Electrical charges and magnetic poles have many similarities but one difference is a opposite magnetic poles repel b one magnetic pole cannot create magnetic poles in other materials c a magnetic pole cannot be isolated d magnetic poles do not produce magnetic fields 2 A soft magnetic material has which property a It cannot be magnetized b It is easy to magnetize c It is hard to magnetize d It attracts slowly moving charges 3 Which of the following is not a hard magnetic material a iron b cobalt c nickel d both b and c 19 2 Earth s Magnetic Field 4 Geophysicists today generally attribute the existence of the Earth s magnetic field to which of the following a convection currents within the liquid interior b iron ore deposits in the crust c nickel iron deposits in the crust d solar flares 5 The term magnetic declination refers to which of the following a angle between Earth s magnetic field and Earth s surface b Earth s magnetic field strength at the equator c tendency for Earth s field to reverse itself d angle between directions to true north and magnetic north 69 Chapter 19 Magnetism 6 The magnetic field of the Earth is believed responsible for which of the following a deflection of both charged and uncharged cosmic rays b deflection of charged cosmic rays c ozone in the upper atmosphere d solar flares 70 Chapter 19 Magnetism 7 The magnetic pole of the Earth nearest the geographic North Pole corresponds to which of the following a a magnetic north pole b a magnetic south pole c a magnetic arctic pole d a magnetic Antarctic pole 8 Which of the following locations has the smallest in magnitude magnetic declination a Washington state b the South Carolina Georgia border c the San Francisco Oakland area d western Colorado 9 The dip angle is a another term for magnetic declination b a measure of the tendency for a compass to point south c close to or at zero near the equator d close to or at zero just north of Hudson Bay 19 3 Magnetic Fields 10 An electron which moves with a speed of 3 0 104 m s parallel to a uniform magnetic field of 0 40 T experiences a force of what magnitude e 1 6 10 19 C a 4 8 10 14 N b 1 9 10 15 N c 2 2 10 24 N d zero 11 The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field a zero b 180 c 90 d 45 12 Assume that a uniform magnetic field is directed into this page If an electron is released with an initial velocity directed from the bottom edge to the top edge of the page which of the following describes the direction of the resultant force acting on the electron 71 Chapter 19 Magnetism a out of the page b to the right c to the left d into the page 13 A proton is released such that its initial velocity is from right to left across this page The proton s path however is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field What is the direction of this field a out of the page b into the page c from bottom edge to top edge of the page d from right to left across the page 14 A proton is released such that it has an initial speed of 4 0 105 m s from left to right across the page A magnetic field of 1 2 T is present at an angle of 30 to the horizontal direction or positive x axis What is the magnitude of the force experienced by the proton qp 1 6 10 19 C a 4 8 10 25 N b 1 3 10 19 N c 3 8 10 14 N d 7 5 103 N 15 A proton moving at a speed of 3 8 106 m s cuts across the lines of a magnetic field at an angle of 70 The strength of the field is 0 25 10 4 T What is the magnitude of the force acting on the proton qp 1 6 10 19 C a 5 1 10 18 N b 9 0 10 18 N c 1 4 10 17 N d 2 3 10 17 N 16 A proton moves across the Earth s equator in a northeasterly direction At this point …