phys 25
A conducting bar is moving downward in a magnetic field pointing down. Which side of the bar is the induced positive charge on? Left There is no induced charge Right Top Bottom
There is no induced charge
Which part of the electromagnetic spectrum listed below is the most particle like? Green light Microwaves Infrared light X-rays
X-rays
A vertical loop is in a magnetic field that is out of the 'page'. If the loop rotates about a horizontal axis does the flux through the loop change? Yes No
Yes
What is the property of the copper in the track that leads to the braking force on the toy car? Copper is magnetic Friction Good thermal conductor Good electrical conductor
Good electrical conductor
The induced current, I, due to an induced emf is I = emf*R I = emf/R I = R/emf None of these are correct
I = emf/R
Vertically polarized light has an intensity of 1000 mW/m2. What is the intensity of the light after passing through a polarizer with an angle of 45° to the horizontal? 0 mW/m^2 707 mW/m^2 500 mW/m^2 1000 mW/m^2 333 mW/m^2
500 mW/m^2
Induced current is current created by Moving a circuit in an electric field A very strong constant magnetic field A changing magnetic field A changing electric field
A changing magnetic field
The electric field and magnetic field of an electromagnetic wave Are perpendicular Are related to the speed of light Are in phase with each other All of these are correct.
All of these are correct
Which of these is not a way to create a changing magnetic field? All of these create a changing magnetic field. Opening or closing a switch in a circuit Moving a circuit relative to a magnet Moving a magnet relative to a circuit
All of these create a changing magnetic field
How are radio waves created? An oscillating dipole causes an oscillating electric field which induces an oscillating magnetic field Not discussed in this chapter An oscillating dipole creates oscillating magnetic and electric fields at the same time. An oscillating dipole causes an oscillating magnetic field which induces an oscillating electric field
An oscillating dipole causes an oscillating electric field which induces an oscillating magnetic field
What magnetic field, B, is needed to create a motional emf for a conductor moving at speed v that is d long. B = vd/emf B = emf/(vd) B = emf*d/v B = emf*v*d
B = emf/(vd)
The force needed to pull a wire along conducting rails in a magnetic field is proportional to B^2 R B None of the above
B^2
A conducting bar is moving downward in a magnetic field pointing toward you (out of the page). Which side of the bar is the induced positive charge on? There is no induced charge Right Left Top Bottom
Bottom
Which animal has 4 types of cones in their eyes? Mouse Dog Chicken Bee
Chicken
A changing electric field Creates an induced magnetic field Creates magnetic monopoles Affects nothing Stops all currents
Creates an induced magnetic field
Which of these equations is correct for the energy of a photon? E = hλ E = hf E = hf/c E = cf
E = hf
A conducting bar is moving to the right on conducting rails that are closed on the right. What direction is the magnetic field around the system if there is a clockwise current induced in the loop? Into the screen Down Up Out of the screen To the right
Into the screen
The speed of an electromagnetic wave Is equal to the speed of light Depends on the frequency Depends on the angle between the electric and magnetic fields Depends on the wavelength
Is equal to the speed of light
The speed of electromagnetic waves Is the same for all waves regardless of wavelength Depends on the wavelength in vacuum Is the same as the speed of sound Depends on the photon energy
Is the same for all waves regardless of wavelength
What property of the trash can blocks radio waves from getting to the radio? The location in the studio. It is ferromagnetic. The color It is a good electrical conductor.
It is a good electrical conductor
What law describes the directions of eddy currents produced when a conductor moves through a magnetic field? Faraday Kirchhoff Ohm Lenz
Lenz
What is the difference between Lenz's Law and Faraday's Law? Lenz's Law determines the magnitude of the induced current, Faraday's determines the direction of the induced current There is no difference, they determine the same thing. These laws are not related. Lenz's Law determines the direction of the induced current, Faraday's determines the magnitude of the induced current
Lenz's Law determines the direction of the induced current, Faraday's determines the magnitude of the induced current
A generator converts Electrical energy into gravitational energy Gravitational energy into mechanical energy Mechanical energy into electrical energy Electrical energy into mechanical energy
Mechanical energy into electrical energy
The potential difference created by moving a conductor in a magnetic field is called Kinetic electric energy Electric potential energy Motional emf Kinetic magnetic energy
Motional emf
Eddy currents are onlyproduced In magnetic materials By changing the magnetic field By moving a conductor in a magnetic field None of these are correct.
None of these are correct
The induced current due to a changing magnetic flux produces a magnetic field which A changing magnetic field does not induce a current. Reinforces the change of the flux Is perpendicular to the change of the flux Opposes the change of the flux
Opposes the change of the flux
The magnetic force on a copper plate moving perpendicular to a narrow localized magnetic field is In the same direction as the motion of the plate Zero. There is no force. Opposite the direction of the motion of the plate More information needed to discuss the force.
Opposite the direction of the motion of the plate
The maximum flux in a rotating loop occurs when the loop itself is At a 45° angle to the field Perpendicular to the field Depends on the shape of the loop. Parallel to the field
Perpendicular to the field
The electromagnetic spectrum consists of X-rays and gamma rays only Radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays and gamma rays Infrared, visible and ultraviolet light only Radio waves and microwaves only
Radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays and gamma rays
When the north pole of the magnet moves toward the copper a magnetic field is induced in the copper. What direction is the force between the copper and the magnet? There is no force - copper is not magnetic Repulsive Attractive
Repulsive
An analog cell phone has a frequency of 850 MHz; a digital phone a frequency of 1950 MHz. Compared to the signal from the analog cell phone, the digital signal has Shorter wavelength and higher photon energy Shorter wavelength and lower photon energy Longer wavelength and higher photon energy Longer wavelength and lower photon energy
Shorter wavelength and higher photon energy
Magnetic flux refers to how much magnetic field goes through a loop. The flux depends on the magnetic field and The effective area of the loop The total area of the loop The length of the loop The width of the loop
The effective area of the loop
The polarization of electromagnetic waves refers to the orientation of The source of the wave The electric field None of these are correct The magnetic field
The electric field
The force needed to maintain a constant velocity of a conduction bar in contact with conducting rails that is moving through a magnetic field depends on The magnitude of the magnetic field The force depends on none of these. The force depends on all of these The length of the bar The speed of the bar.
The force depends on all of these
A horizontal loop of wire is above a vertical magnet with its north pole on top. The magnet moves closer to the loop. What can be said about an induced current in the wire loop? There is not enough information to say anything The induced current is counterclockwise There is no induced current in the wire loop. The induced current is clockwise
The induced current is clockwise
A magnetic field is directed into the page in a specific area. A wire loop is perpendicular to the field and is slowly moved out of the area with the field. Which is true? Not enough information to say. There is no induced current in the loop. The induced current is counterclockwise The induced current is clockwise
The induced current is clockwise
Changing the angle of a wire loop relative to a magnetic field changes The magnetic field Nothing The size of the loop The magnetic flux
The magnetic flux
Faraday's law of electromagnetic induction helps determine The direction of induced currents and emfs. The direction and magnitude of induced emfs only The magnitude of induced emfs and currents The direction and magnitude of induced currents only
The magnitude of induced emfs and currents
A cell phone emits EM waves at 1.9 GHz and a microwave oven emits EM waves at 2.4 GHz. Which one emits the shorter wavelength? The cell phone The microwave oven They emit the same wavelength
The microwave oven
Your cell phone uses 1.9GHz frequency electromagnetic waves. A microwave oven uses 2.4 GHz frequency electromagnetic waves. What can you say about the wavelengths of these waves? Not enough information to say anything about the wavelengths The waves from both have the same wavelength The waves from the oven have a longer wavelength The waves from the phone have a longer wavelength
The waves from the phone have a longer wavelength
The circuit is constructed so that the blue LED comes on if the current is in one direction and the orange LED comes on if the current is in the other direction. The blue LED comes on when the magnet is quickly placed on the coil. As the magnet is quickly removed from the coil what will happen? Both LED's come on. The blue LED comes on The orange LED comes on. No LED comes on
The orange LED comes on
A photon is A figment of Einstein's imagination The particle aspect of an electromagnetic wave Not in this chapter A positively charged part of an atomic nucleus
The particle aspect of an electromagnetic wave
Which laser pointer (red or violet) outputs the higher energy photons? The violet laser It depends on the width of the beam They have the same intensity so the same energy The red laser
The violet laser
Which part of the electromagnetic spectrum can damage DNA? Radio All of these damage DNA Ultraviolet Infrared
Ultraviolet
The parts of the electromagnetic spectrum that can ionize molecules and/or atoms are Infrared and visible light Ultraviolet only X-rays and gamma rays only Ultraviolet, x-rays and gamma rays
Ultraviolet, x-rays, and gamma rays