Reading Quiz

Question 1:

Answer:

1. 1. Move a bar magnet in the presence of a coil loop. 2. Move a coil loop in the presence of a bar magnet. 3. Move a 2nd coil, containing an electric current, in the presence of the coil loop. 4. Turn the current on or off in a circuit that is in the presence of the coil loop.
2. 1) Move a bar magnet near a stationary coil. 2) Move a coil near a stationary magnet. 3) Move a coil through which current is flowing near first coil.
3. (1) move a magnet near a wire coil-ammeter circut that contains no current (2) move a current carrying circut near a non-current carrying circut (3) hold a current carrying circut and a non-current carrying circut stationary and open and close the current-carrying circut's switch
4. moving a bar magnet in the middle of a coil of wire move a coil near a stationary magnet move a coil of wire with a current going through it towards a stationary coil of wire
5. One way is to move a magnet toward the coil. Another way is to move another coil that is carrying a steady current from a battery, and therefore producing a magnetic field, and moving it toward the coil. A third way is to have a coil, such as the one in the second scenario, with a switch, and then opening the switch, which will result in a current in a coil loop in the other coil loop.
6. Current in a coil loop can be induced first from the movement of a magnet in the presence of a wire coil. It can also be produced from a coil that has a steady battery-supplied current, and is held near a coil with no supplied current, inducing a current in the latter coil. A final way is through moving the coil near the magnet, basically an opposite of what was done in the first induction.
7. move a bar magnet toward/away from a coil loop, or move a coil loop oward/away from a bar magnet replace the bar magnet with a current-carrying circuit (electric magnet) in the above situation change the current in an adjacent circuit, this circuit is beside the coil loop (what is an adjacent circuit? I understand the graph in the book, but I want the world explaination of "adjacent circuit")
8. Move something like magnet (whatever creates magnetic field) near the coil. Move the coil instead of moving the magnet. Put a circuit with a switch next to the coil and turn it on (or off).
9. 1. move a magnet towards the coil loop 2. move the coil loop towards a magnetic filed 3. move another loop with a current induced by a battery towards the coil loop
10. Move a magnet within the loop, move the loop around a magnet, or move the coil near another coil that's carrying current from a battery.
11. Move a magnet, with the north to the right, towards a coil. Move a magnet, with the north to the right, away from a coil. Move a coil towards a stationary magnet.
12. Move a magnet near a coil loop. Move the coil loop near a magnet. Place the coil loop near another loop which holds changing current.
13. 1)Move a bar magnet towards a coil loop 2)Move the coil loop towards a bar magnet 3)Move a current carrying loop towards the coil loop
15. Move a magnet towards or away from a coil, move another coil carrying a steady current towards or away from a coil, or turn off the steady current to another coil while near the first coil.
16. move a bar magnet near the coil; move the coil near a stationary bar magnet; move another coil with current running through it near the first coil
17. 1. Have a difference in voltage over a closed loop 2. Have a magnetic field change over a closed loop of current 3. Have the area enclosed by a closed loop of current vary

Question 2:

Answer:

1. An induced emf is an emf that is not constant emf like a battery. Instead it is cause by an electromagnetic field. Either magnets and circuits can be induced emfs.
2. I don't think the book ever really defines it. I'm going to ask you about it tomorrow. But Faraday's law informs us that it is equal to the rate of change of the magnetic flux.
3. An induced emf is not one that is found centralized/localized, like in a battery, but instead it is one that is spread out in the conductors that make up the circut.
4. the emf present when an induced current is created. the emf is spread out throughout the conductors in a circuit instead of localized in normal situations, such as in a battery
5. Induced emf is the electro-motive force that is created from some outside source rather than a battery. It is not usually localized and might spread throughout the conductors in a circuit.
6. Induced emf is a concept brought about by the rate that the magnetic flux is changing.
7. a force to drive current in a circuit, or move the electrons in an closed circuit. quote from book: "it takes a source of emf, such as a battery, to drive current in a circuit"
8. Induced emf isn't localized as the emf with a battery.
9. The emf is the electric force from the electric field that is created by a changing magnetic field
10. This is the force created by a moving magnet/coil or charge/coil combination; the movement of electrons that creates a field.
11. Induced emf is proportional to the rate of change of flux and creates a magnetic force to oppose the change.
12. Induced emf means the electro motive force in a loop is created by another material which changes the magnetic field around the loop.
13. induced emf is inducing a current without a battery
15. Induced emf is the electromotive force that results from an induced current. It is usually spread through the conductors making up the circuit.
16. Induced emf refers to energy driving a current that does not come from an element within the circuit, but from a changing external magnetic field.
17. It is voltage induced by the movement of a magnetic field.

Question 3:

Answer:

1. The negative sign represents the fact that the induced emf creates an opposite sign in whatever it is inducing a charge in. This is what Lenz's law says.
2. When you push a magnet toward a coil, the induced current is such that the magnetic field it creates opposes that of the bar magnet. So if you push the bar magnet toward the coil north end first, then the magnetic field caused by the current in the coil will point toward the magnet.
3. The negative sign in Faraday's law helps to represent that the induced emf opposes the change in flux.
4. The fact that the induced emf tends to oppose the change in flux
5. It represents the fact that the induced emf tends to oppose the change in flux.
6. The negative sign is a result of the fact that the induced emf generally opposes the change in flux, so the direction is opposite (like friction).
7. the induced emf tends to oppose the change flux, and in SI the proportionality between emf and rate of change of flux is -1
8. The proportionality between emf and the rate of change in flux.
9. The negative sign in Faraday's law represents the fact that an increase in flux causes an emf in the opposite direction of that increase of flux.
10. The proportionality constant between emf and the rate of change of the flux; because induced emf usually opposes change of flux.
11. It represents the fact that the induced current will always form a magnetic force to oppose the change of flux, and this force will be opposite to the magnetic force created by the moving magnet.
12. Negative sign means induced emf opposes the change in flux.
13. The rate of change of the flux carries the opposite sign as the emf
15. The negative sign represents that the induced emf is in the opposite direction of the change in magnetic flux.
16. The negative sign represents the fact that the induced emf opposes the change in magnetic flux that causes it.
17. The vector direction of the induced emf is opposite from the direction of the magnetic flux lines.

Question 4:

Answer:

1. Infinite amounts of energy? When an induced emf is moved towards a wire loop, the wire loop would become charged with the same sign as the induced emf, so it would attract the induced emf. The problem with this is that when an induced emf induces a charge, it is doing work on whatever it is charging, but if the thing it was charging was doing work back on the emf to pull it closer, then they would both be gaining energy, and this violates the laws of conservation of energy.
2. Conservation of energy would be null and void.
3. If there were a positive sign in Faraday's Law of Induction, then the equation would only give you the magnitude of the emf, and not its direction. Also, it would then be suggesting that you had to do negative work in order to overcome the magnetic force, giving you something for nothing which is impossible.
4. there would be no work done on the magnet/coil system and so the coil would never heat up
5. If the sign were positive, an increase in magnetic flux would then increase the induced emf. According to Lenz's Law, current in a loop would continually grow stronger if a magnet were moved toward it due to the increasing strength of the magnetic field, which would grow stronger by increasing currents. Therefore, infinite currents in circuits would be possible by simply moving magnets.
6. If there were a positive sign in Faraday's law of induction, the directions would be changed of magnetic poles and the way that we show these directions.
7. by change the rate of change of magnetic flux through any surface bounded by the circuit, the induced emf in a circuit also changes in the same direction
8. The magnetic field is getting weaker.
9. If the sign were positive, then you would be doing no work by moving the magnet in the loop, thus no energy would be created
10. The law would produce the change in flux instead of emf.
11. The law of conservation of energy would be disproven.
12. Energy conservation won't hold here.
13. If there were a positive sign on Faradays law, you could induce a current in a loop without doing any work on a magnet, essentially creating free energy.
15. If the sign was positive, you could add energy to any loop without doing any work. This would break many laws of physics and thermodynamics.
16. If there was a positive sign in Faraday's law, it would not require positive work to be put into the system to produce the change in flux that produces the current, which would mean you were creating energy from nothing.
17. Currents induced by magnetic fields would create more magnetic fields in the same direction, which would induce more current, which would violate conservation of energy.

Question 5:

Answer:

1. Eddy currents are any temporary currents induced by an induced emf.
2. Eddy currents make it hard to move any conductor in the presence of a changing magnetic flux. They create what the book describes as a type of "magnetic friction." They make elliptical machines and metal detectors work.
3. An eddy current is an induced current that dissipate energy and accumulate in solid conductors that experience a change in magnetic flux. They are used commonly to provide resistance in exercise machines and in metal detectors.
4. The induced currents created in a solid conductor when you move the conductor into and out of a magnetic field or when the magnetic flux changes around the conductor.
5. Eddy currents are currents in a conductor produced by a changing magnetic field that in turn causes a flow of charge in the conductor which, according to Lenz's Law, opposes the change in the magnetic field. They are responsible for a type of resistance that makes it harder to move a conductor in a magnetic field.
6. Eddy currents are currents induced in small sections of a large solid conductor that has an inherently low resistance; they can also dissipate energy rapidly.
7. Eddy currents are induced in any conducting material that comes between the two coils, and the direction of the induced currents is always to reduce the changing flux
8. Eddy current is a solid conductor which can create a magnetic field braking rapid actions of stuff like saw blades or wheels.
9. An eddy current is a current produced in a material with low resistance, that produces a large current, and thus makes motion through the magnetic field difficult
10. They are like a form of magnetic friction; when induced, they can dissipate magnetically created kinetic energy.
11. Cuurents induced in a conductor by a changing manetic flux.
12. Eddy current is an induced current in conductors which consumes energy and makes the conductor harder to move in magnetic field.
13. Eddy currents are induced currents inside solid conductors. With the right conductors this leads to a dissipation of power.
15. Eddy currents are induced currents in solid conductor materials that dissipate energy when the conductor is attempting to move into or out of a magnetic field.
16. Eddy currents are the currents produced within solid conductors when they are subjected to a changing magnetic field. These differ from the currents in a circuit because the conductor does not define a physical loop through which the current flows; the current simply makes its own loops within the solid object.
17. A changing magnetic flux over a solid conductor creates small currents whose magnetic fields oppose the main field, thus resisting motion.

Question 6:

Answer:

1. Positive and negative charges build up on opposite sides of it.
2. There is a build up of charge. It's like the current flows and then it has to stop, so on one side of the "break" there's a build up of positive charge, and on the other side, there's a build up of negative charge.
3. When an open loop is placed in a magnetic field, positive charges accumulate neear one end, and negative charges accumulate near the other. This creates a potential difference, which is equal to the emf.
4. negative charges build up on one side of the break and positive charges build up on the other side of the break, and eventually so much charge builds up that the potential difference across the gap opposes the induced emf, which results in a state in which the gap voltage equals the induced emf
5. Positive charge would accumulate at one end while negative charge would accumulate at the other. It continues until the gap voltage from the built up charges opposes the induced emf and a steady state where the two are equal is reached.
6. The gap voltage, or the voltage over the break, will equal the induced emf, as a result of build up of opposite charges at each end of the gap.
7. due to the magnetic field effects, all positive charges is going to accumulated at one end and the negative charges at the other. the gap voltage between two ends equals the induced emf
8. Positive charge will be pushed to one of the end of the open circuit, and negative ones will be in the other end.
9. A potential difference is created at the break equal to the emf
10. The ends of the circuit build up charge, due to the emf induced by the changing field.
11. When this opening appears, the positive charges gather at on end and the negative charges gather at the other. The pd built up due to this gathering opposes the induced emf's tendency to move charge. This gives a steady state in which the gap voltage equals the induced emf.
12. Charges will build up at the gap until potential difference of the gap is equal to induced emf.
13. A voltage builds up between the ends of the break in the coil until the gaps voltage equals the induced emf
15. In a changing magnetic field, charge builds up at the gap of the open circuit.
16. Current attempts to flow in a direction that would oppose the change in the external magnetic field, until enough charge builds up on the two disconnected ends to create a potential difference great enough to stop the motion of any more charge.
17. There is no current, though a difference in potential still arises.

Question 7:

Question 8: