Chapter Questions Exam 3 Review

In a simplified model of the hydrogen atom, its electron moves in a circular orbit with a radius of 5.3×10^−10 m at a frequency of 6.6×10^15 Hz. What magnetic field would be required to cause an electron to undergo this same motion?

B = f2πm/q (rearranged from f = Bq/2πm) f = 6.6×10^15 Hz m = mass of electron, 9.1x10^-31 q = charge of proton/electron (the same # for both), 1.6x10^-19 B = 2.35x10^5 T

A particular coil has 100 turns and a diameter of 6.0 m. When it's time for a measurement, a 7.0 A current is turned on. The large diameter of the coil means that the field in the water flowing directly above the center of the coil is approximately equal to the field in the center of the coil. The field is directed downward and the water is flowing east. The water is flowing above the center of the coil at 1.5 m/s . What is the magnitude of the field at the center of the coil?

B = uNI/L u = 1.26x10^-6 I = 7 A L = 6 m B = 1.47x10^-4 T

The human eye is most sensitive to light in the yellow-green region of the electromagnetic spectrum (frequency of 550 THz). What is the energy of one yellow-green photon? Use h = 4.14×10^−15 eV⋅s.

E = hf h = 4.14x10^-15 f = 550x10^12 E = 2.28 eV

A particular coil has 100 turns and a diameter of 6.0 m. When it's time for a measurement, a 7.0 A current is turned on. The large diameter of the coil means that the field in the water flowing directly above the center of the coil is approximately equal to the field in the center of the coil. The field is directed downward and the water is flowing east. The water is flowing above the center of the coil at 1.5 m/s . What is the magnitude of the force on an ion with a charge +e?

F = B*v*q B = 1.47x10^-4 v = 1.5 m/s q = 1.6x10^-19 (charge of proton/electron (the same # for both) F = 3.5x10^-23 N

The unit of current, the ampere, is defined in terms of the force between currents. Two 1.0-meter-long sections of very long wires a distance 2.0 m apart each carry a current of 1.0 A What is the force between them? (If the force between two actual wires has this value, the current is defined to be exactly 1 A).

F = u*i1*i2*L/2πr u = 4π*10^-7 I1 = 1 I2 = 1 L = 1 r = 2 F = 1.0x10^-7 N

A) Right hand rule = b B) Right hand rule = from a --> b C) E = vB v = 7 B = 0.4 E = 2.8 eV D) b has higher potential. E) V = EL E = 2.8 L = 35 (35x10^-2) V = 0.98 V F) 0.98 V

In the figure, a conducting rod of length L = 35.0 cm moves in a magnetic field B of magnitude 0.400 T directed into the plane of the figure. The rod moves with speed v = 7.00 m/s in the direction shown. A) When the charges in the rod are in equilibrium, which point, a or b, has an excess of positive charge? B) What is the direction of the electric field in the rod? C) When the charges in the rod are in equilibrium, what is the magnitude E of the electric field within the rod? D) Which point, a or b, has a higher potential? E) What is the magnitude Vba of the potential difference between the ends of the rod? F) What is the magnitude E of the motional emf induced in the rod?

The aurora is caused when electrons and protons, moving in the earth's magnetic field of ≈ 5.0×10^−5T, collide with molecules of the atmosphere and cause them to glow. What is the frequency of the circular orbit for a proton with speed 5.0×10^4 m/s?

f = Bq/2πm B = 5.0x10^-5 q = charge of proton/electron (the same # for both), 1.6x10^-19 m = mass of proton, 1.67x10^-27 f = 762 Hz

The aurora is caused when electrons and protons, moving in the earth's magnetic field of ≈ 5.0×10^−5 T, collide with molecules of the atmosphere and cause them to glow. What is the frequency of the circular orbit for an electron with speed 1.0×10^6 m/s? Assume that the electron moves in a plane perpendicular to the magnetic field.

f = Bq/2πm B = 5.0×10^−5 q = charge of proton/electron (the same # for both), 1.6x10^-19 m = mass of electron, 9.1x10^-31 f = 1.39x10^6 Hz

A particular coil has 100 turns and a diameter of 6.0 m. When it's time for a measurement, a 7.0 A current is turned on. The large diameter of the coil means that the field in the water flowing directly above the center of the coil is approximately equal to the field in the center of the coil. The field is directed downward and the water is flowing east. The water is flowing above the center of the coil at 1.5 m/s . What is the direction of the force on a positive ion in the water above the center of the coil? A) The force points north. B) The force points east. C) The force points south. D) The force points west.

A) The force points north.