Дидактические материалы для работы с учебным пособием С.В. Андриановой «English Thesaurus of Student-Physicist». Учебно-методическое пособие
.pdfsplits, equals all of the current flowing out of the same junction. That's to say that what goes in must come out.)
8.What does the amount of current passing through a branch depend on? (Its respective resistance.)
9.Why if you added more bulbs in series, you’d see that the brightness would keep decreasing for each additional bulb? (Since identical light bulbs have identical resistances, this corresponds to a current that’s shared between the bulbs. So the brightness would keep decreasing for each additional bulb.)
10.What will happen with the bulbs in a parallel connection? (Their brightness will be the same.)
Exercise 3. Give examples of using different sources of emf in our everyday life. /batteries, generators, etc./
Exercise 4. Are the following statements true (T) or false (F)?
Capacitors are not used to construct electric circuit. (F)
Terminal voltage is less than ideal emf potential. (T)
In a closed circuit a current is maintained by a source of emf. (T)
A person can be electrocuted by touching a live wire. (T)
Living organisms do not use electric phenomena. (F) /Neurons form a complex network. They produce voltage pulses./
Exercise 5. Give your comments on the following statement, speak about advantages/disadvantages; your attitude; history of the invention; the way and prospects of using; being ecological-friendly etc.:
The issue of recycling used batteries is of high importance.
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Unit 19
MAGNETISM
Exercise 1. Follow the link and watch the video:
https://www.youtube.com/watch?v=s94suB5uLWw
Exercise 2. Answer the questions:
1.Describe Oersted's /’ǝ:sted/ experiment with the compass. (He was using a compass and an electric wire for a demonstration. He turned on the current that ran through the wire and noticed that the needle in the compass started to move, when he turned the current off the needle returned to where it had been. Then he ran the current through a wire in the opposite direction and saw the needle moved the other way.)
2.What did he discover? (fundamental discovery: the connection between electricity and magnetism)
3.When did the discovery happen? (1820.)
4.Where is it used today? (in much of the technology that is used today: from hydroelectric dams to smartphones)
5.What are the basics of magnetism? (They have a North and South pole. Two of the same poles will repel each other, while opposites attract.)
6.What materials can be magnets? Why? (Only special materials, especially those that contain iron, can be magnets. It depends on their molecular properties.)
7.Why can we use compass to figure out which way is north? (There is a magnetic field around earth. The magnet in the compass aligns itself with earth's magnetic field)
8.How are we being protected from the solar radiation? (The sun is constantly shooting radiation towards Earth in the form of charged particles. Earth has a magnetic field.
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Currants are made up of moving electric charges, so a magnetic field would also exert a force on single electric chargers that pass through it. That is what the Earth's magnetic field does to charged particles coming from the sun: it deflects them.)
9.What are the four factors that affect the magnitude of the force? (the current in the wire, the length of the wire running through the magnetic field, the magnetic field (B), the sine theta /The closer to perpendicular the current is with respect to the magnetic field’s direction, the stronger the force is. The sine maximum value is 1, when theta is 90 degrees/.)
10.What does the equation for the force of a magnetic field on a current say? (It says that the strength of the force is equal to the current, times the length of the wire, times the strength of the magnetic field, times the sine of the angle between the current and the magnetic field.)
Exercise 3. Read the formula: F = q v B sinΘ /F equals q v B sine theta/ What formula is it? /the force on a single electric charge/
Exercise 4. Are the following statements true (T) or false (F)?
North and south poles of a magnet can exist in isolation of each other. (F)
The needle in a compass is horizontal with respect to Earth’s surface near the equator. (T)
A current-carrying conductor produces a magnetic field.
(T)
A stationary charged particle doesn’t interact with a static magnetic field. (T)
In ferromagnetic materials there is strong coupling between neighboring atoms. (T)
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Exercise 5. Give your comments on the following statement, speak about your attitude; history of the phenomenon etc.:
Earth’s magnetic poles have shifted several times. Now they are said to be shifting again. What consequences shall we wait?
Unit 20
INDUCED VOLTAGES AND INDUCTANCE
Exercise 1. Follow the link and watch the video:
https://www.youtube.com/watch?v=pQp6bmJPU_0
Exercise 2. Answer the questions:
1.What was one of the biggest discoveries of the 19th century? (Electric currents can create magnetic fields./and vice versa/)
2.Who was able to detect electric currents induced by magnetic fields? (Joseph Henry and Michael Faraday, both on their own.)
3.How did Faraday notice that a constant magnetic field didn’t cause an electric current in a loop of wire? (When he turned the current on and off in the first coil, there was a brief spike of current in the second coil – but only while the current was changing from off to on and back again.)
4.What does Faraday’s Law of Induction say? (It says that a changing magnetic field will induce an emf in a loop of wire.)
5.What causes electrons to move and form a current? (emf, which stands for electromotive force)
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6.What other things induce emf? (Changing the area of the loop of wire and changing the angle between the loop and the magnetic field.)
7.What is essentially a measure of the magnetic field running through a loop of wire? (Magnetic flux.)
8.What are three factors that affect the magnetic field? (First, there’s the strength of the magnetic field, which we label as B. Next, there the area of the loop, A. And finally, there’s the angle, theta, between the magnetic field and a line perpendicular to the face of the loop.)
9.When do we use Lenz’s /’lenzis/ Law? (to figure out in what direction will the induced current flow)
10.What does it say? (Lenz’s law says that the magnetic field generated by the induced current will be in the direction opposite the change magnetic flux.)
Exercise 3. Read the formula: /Tesla meter squared equals a weber. Magnetic flux is measured in units of Tm2, also known as webers (SI unit)./
Exercise 4. Are the following statements true (T) or false (F)?
An emf is induced in a circuit when the magnetic flux through the circuit changes with time. (T)
The SI unit of inductance is the Tesla /T/ (F – the henry (H)).
The battery has to do work to produce a current. (T)
When the switch is opened, the current immediately falls to zero. (F) /It doesn’t immediately falls to zero because of self-induction./
The AC generator is a device that converts mechanical energy to electrical. (T)
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Exercise 5. Give your comments on the following statement, speak about advantages/disadvantages; your attitude; history of the invention; the way and prospects of using; being ecological-friendly etc.:
For superconductors and nanoantennas kinetic inductance is very important and can’t be neglected in calculations. In this case nanoantennas can be used as quantum communication lines. What are the prospects?
Unit 21
ALTERNATING CURRENT CIRCUITS
AND ELECTROMAGNETIC WAVES
Exercise 1. Follow the link and watch the video:
https://www.youtube.com/watch?v=Jveer7vhjGo
Exercise 2. Answer the questions:
1.Describe the voltage and current in direct current circuits. (The voltage source in a DC circuit is unchanging, so the current will be constant, too.)
2.Describe the voltage and current in an AC circuit. (Both the voltage and the current are constantly changing directions, from positive to negative and back again.)
3.What variable represents the value for the current itself? (That variable is the root-mean-squared, or RMS value, of current.)
4.What do we use them for? (To better describe current and voltage in AC circuits.)
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5.What is called self-inductance? (The induction of an emf that opposes the main current.)
6.What units is inductance expressed in? (Henrys/H/, Joseph Henry discovered self-inductance.)
7.How are inductors designed? (They are coils that are designed to maximize their self-inductance.)
8.When are the voltage and current peaks in phase? (Since the voltage and current peaks occur at the same time, the two are said to be in phase.)
9.Is it true for inductors and capacitors? (No. In AC circuit inductors, we say that the current and voltage are out-of- phase, which means they don’t peak at the same time.
Capacitors in AC circuits are also out of phase, but for a different reason. Current in resistors is in phase with voltage. And current in capacitors lags voltage.)
10.Which part of an AC circuit dissipates power as thermal energy? (the resistance)
https://www.youtube.com/watch?v=K40lNL3KsJ4
1.What is Maxwell's first equation based on? (Gauss's law and electric flux)
2.What does "a closed surface" mean here? (any surface of any shape that completely loses a charge)
3.What is a permittivity of free space? (a constant of proportionally? that relates electric charge to the physical effect of electric fields)
4.What is the difference between the first and the second Maxwell's law? (in the second the magnetic flux and Gauss's law are used)
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5.What law is used in the 3d Maxwell's equation? (Faraday's law but slightly different)
6.What does Faraday's law of induction say? (a changing magnetic field will induce an electromotive force in a loop of wire)
7.What is light? (an electromagnetic wave)
Exercise 3. Give examples of using electromagnetic waves in everyday life. (wireless charge)
Exercise 4. Are the following statements true (T) or false (F)?
Current in resistors is in phase with voltage. (T)
Current in capacitors lags voltage. (T)
Rmc current is a special kind of average value ofcurrent.
(T)
Back emfs always oppose the change in resistance. (F) /change in the current/
We cannot change a small AC voltage to a larger one. (F)/We can (with a transformer)./
Exercise 5. Give your comments on the following statement, speak about advantages/disadvantages; your attitude; history of the invention; the way and prospects of using; being ecological-friendly etc.:
What’s your attitude towards 5G-net standard? There are some people protesting. What reasons can you think of to support the idea? Can it be dangerous?
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Unit 22
REFLECTION AND REFRACTION OF LIGHT
Exercise 1. Follow the link and watch the video:
https://www.youtube.com/watch?v=Oh4m8Ees-3Q
Exercise 2. Answer the questions:
1.How many rays can a light source emit? (A light source may be emitting an infinite number of rays.)
2.How do you see an image if you’re viewing something in a reflection? (You see it reversed.)
3.At what angle do rays leave the reflected surface? (At the same angle at which they struck it.)
4.What do we call the law of reflection? (The fact that the angle of reflection is equal to the angle of incidence.)
5.What happens when light rays change from one medium to another? (The phenomenon called refraction, when light rays change direction at the interface between media.)
6.What does Snell’s Law say? (It says that angles of refraction are determined by the index of refraction for each medium and the angle of incidence.)
7.What is the index of refraction for a certain medium equal
to? (It is the ratio of the speed of light in a vacuum versus the speed in that medium.)
8. What happens when a ray enters a medium with an increased index of refraction? (The angle of refraction decreases.)
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9.When is an image considered to be real? (if the rays from an object converge at some location, such as your eye or on some other surface, like a film.)
10.When you look in the mirror what image do you see? (a virtual - an image where the light rays don’t actually converge, so your eyes construct an image as if the diverging rays originated from a single point.)
Exercise 3. Give examples of converging and diverging lenses.
(a camera, binocular, magnifying glass)
Exercise 4. Are the following statements true (T) or false (F)?
Light may act either like a particle or like a wave. (T)
The wave theory of light explains the laws of reflection and refraction. (T)
“Red eye” effect in photographs occurs due to retroreflection. (T)
The angle of reflection is proportional to the angle of incidence. (F) /equals/
Light travels in a curve-line path in a homogeneous medium. (F) /in a straight-line path/
Exercise 5. Give your comments on the following statement, speak about advantages/disadvantages; your attitude; history of the invention; the way and prospects of using; being ecological-friendly etc.:
Fiber-optic Internet lines and devices are much faster compared to wires.
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