Presentation on physics electromagnetic induction. Presentation on the topic "Electromagnetic induction. Faraday's experiments." The phenomenon of electromagnetic induction






“Convert magnetism into electricity...” The English physicist Michael Faraday, having learned about Oersted’s experiments, set himself the task of “converting magnetism into electricity.” He solved this problem for 10 years - from 1821 to 1831. Faraday proved that a magnetic field can generate electricity.


The importance of EMR for physics and technology The action of electric current generators at all power plants on Earth is based on the phenomenon of EMR. German physicist Heinrich Helmholtz said: “As long as people enjoy the benefits of electricity, they will remember the name of Faraday.”










Based on Faraday's experiments, we can conclude under what conditions the EMR phenomenon can be observed: The phenomenon of electromagnetic induction consists in the occurrence of an induced current in a closed circuit when the magnetic flux changes through an area limited by the circuit.






Change over time of the magnetic field in which the circuit is at rest. Induction current in a stationary closed circuit located in an alternating magnetic field is caused by the electric field generated by the alternating magnetic field (eddy electric field)






The phenomenon of electromagnetic induction

“Happy accidents come only to one portion of the prepared mind.”

L. Pasternak


The experience of the Danish scientist Oersted

1820

1777 – 1851






Michael Faraday

1791 – 1867, English physicist,

Honorary member of the St. Petersburg

Academy of Sciences (1830),

Founder of the doctrine of the electromagnetic field; introduced the concepts of “electric” and “magnetic field”;

expressed the idea of ​​existence

electromagnetic waves .

1821 year: “Convert magnetism into electricity.”

1931 year – received electric current using a magnetic field



"Electromagnetic induction" -

Latin word meaning " guidance"


M. Faraday's experiment

“A copper wire 203 feet long was wound on a wide wooden spool, and between its turns was wound a wire of the same length, insulated from the first with a cotton thread.

One of these spirals was connected to a galvanometer, the other to a strong battery...

When the circuit was closed, a sudden but extremely weak action was observed on the galvanometer, and the same effect was observed when the current was stopped.

With the continuous passage of current through one of the spirals, it was not possible to detect deviations of the galvanometer needle ... "



What do we see?

Conclusion from the experience :

  • The current arising in the coil (closed circuit) is called

induction.

  • The difference between the resulting current and what we previously knew is that to receive it no current source needed.

Faraday's general conclusion

Induction current in a closed loop occurs when the magnetic flux changes through the area limited by the loop.


Electromagnetic induction is a physical phenomenon consisting in the occurrence of an electric current in a conducting circuit, which is either at rest in a time-varying magnetic field, or moves in a constant magnetic field in such a way that the number of magnetic induction lines penetrating the circuit changes.

The current that arises is called induction .





What is the reason for the occurrence induced current in the coil?


Consider a magnet:

What can you say about the magnet?


When we introduce a magnet into the closed circuit of a coil, What changes for him?


How to determine the direction of the induction current?

We see that the direction of the induction current is different in these experiments.






Based on the law of conservation of energy, the Russian scientist Lenz offered rule , which determines the direction of the induction current.

Russian physicist Emil Lenz

1804 – 1865




0, if it extends, then ∆Ф 0). 3. Determine the direction of the induction lines of the magnetic field B′ created by the induced current (if ∆Ф 0, then lines B and B′ are directed in opposite directions; if ∆Ф 0, then lines B and B′ are co-directed). 4. Using the gimlet rule (right hand), determine the direction of the induction current. ∆ Ф is characterized by a change in the number of lines of magnetic induction B penetrating the circuit "width="640"

1. Determine the direction of the induction lines of the external field B (coming from N and are included in S ).

2. Determine whether the magnetic flux through the circuit increases or decreases (if the magnet moves into the ring, then ∆Ф 0, if extended, then ∆Ф 0).

3. Determine the direction of the induction lines of the magnetic field B′ created by the induction current (if ∆Ф 0, then lines B and B′ are directed in opposite directions; if ∆Ф 0, then lines B and B′ are codirectional).

4. Using the gimlet rule (right hand), determine the direction of the induction current.

∆ F

characterized by change

number of lines of magnetic induction B,

permeating the contour




Mathematical formula for the law of electromagnetic induction

ε = - ΔΦ/Δ t 

ΔΦ/Δ t - rate of change of magnetic flux (units Wb/s )

The induced emf in a closed loop is equal in magnitude to the rate of change of the magnetic flux through the surface bounded by the loop.


Electromagnetic law induction

The EMF of electromagnetic induction in a closed loop is numerically equal and opposite in sign to the rate of change of the magnetic flux through the surface bounded by this loop.

The current in the circuit has a positive direction as the external magnetic flux decreases.












Computer hard drive.

Electromagnetic induction in the modern world

Video recorder.

Policeman detector.

Metal detector at airports

Magnetic levitation train

Showing videos about the application of the phenomenon of electromagnetic induction: metal detector, recording information on magnetic media and reading from them - disk “Physics grades 7-11. Library of visual aids" Educational complexes.

Municipal educational institution

"Secondary school No. 72"

Electrodynamics Electromagnetic induction

(Part 1)

Prepared the presentation

physics and computer science teacher

V.S. Dubovik

Saratov


Electromagnetic induction

In this lesson you should study the following questions:

  • the phenomenon of electromagnetic induction;
  • difference between alternating electric and magnetic fields and constant ones;
  • magnetic flux;
  • direction of induction current;
  • Lenz's rule;
  • law of electromagnetic induction;
  • vortex electric field;
  • induced emf in moving conductors;
  • application of the phenomenon of electromagnetic induction.

As a result, you should learn:

  • determine the direction of the induction current of magnetic induction;
  • calculate magnetic flux;
  • calculate the induced emf.

For this:

  • Study the textbook materials;
  • Answer the self-control questions;
  • Consider the methodology for solving problems of this type;

Discovery of the phenomenon of electromagnetic induction

MICHAEL FARADAY

(1791-1867)

Engraving: Michael Faraday giving a lecture demonstrating his experiments at the Royal Institution in London in 1830


Observing the phenomenon of electromagnetic induction

The phenomenon of the occurrence of EMF in a circuit when the magnetic flux passing through the circuit changes is called electromagnetic induction.


Magnetic flux. Law of Electromagnetic Induction

Magnetic flux Φ through the area S contour is called the value:

Φ = B · S cos α

The SI unit of magnetic flux is called vberom (Wb). A magnetic flux equal to 1 Wb is created by a magnetic field with an induction of 1 T, penetrating in the normal direction a flat contour with an area of ​​1 m 2 .

Faraday experimentally established that when the magnetic flux changes in a conducting circuit, an induced emf E arises ind , equal to the rate of change of the magnetic flux through the surface bounded by the contour, taken with a minus sign:


0, and the EMF ind I ind flows towards the selected positive direction of bypassing the circuit. Lenz's rule reflects the experimental fact that EMF ind and ΔФ/Δt always have opposite signs (the “minus” sign in Faraday’s formula). Lenz's rule has a deep physical meaning - it expresses the law of conservation of energy." width="640"

Direction of induction current. Lenz's rule

Experience shows that the induction current excited in a closed loop when the magnetic flux changes is always directed in such a way that the magnetic field it creates prevents the change in the magnetic flux that causes the induction current. This statement is called Lenz's rule (1833).

Lenz Emily Khristianovich

Illustration of Lenz's rule.

In this example, ΔФ/ Δ t 0, and the EMF ind I ind flows towards the selected positive direction of bypassing the circuit.

Lenz's rule reflects the experimental fact that EMF ind and ΔФ/Δt always have opposite signs (the “minus” sign in Faraday’s formula). Lenz's rule has a deep physical meaning - it expresses the law of conservation of energy.


Induction EMF in moving conductors

The occurrence of induced emf is explained by the action of the Lorentz force on free charges in moving conductors. The Lorentz force plays the role of an external force in this case.

Work done by force F L on the path l equal to A = F L · l= eυB l .

According to the definition of EMF

The relationship for EMF ind can be given the usual form. Over time Δt, the contour area changes by ΔS = lυΔt. The change in magnetic flux during this time is equal to

ΔΦ = BlυΔt. Hence,


Problem solving


Problem solving

B i


Problem solving


Problem solving


Problem solving


Problem solving


Problem solving


Problem solving


Problem solving

The “-” sign can be ignored because not specified

how the magnetic flux changes.


Problem solving


Problem solving


Problem solving


Problem solving


Homework

§§ 11.13, Ex.2 (8.9)

Consider all problems from the trial versions of the Unified State Exam for 2006 - 2009. on the topic of electromagnetic induction.

ELECTROMAGNETIC INDUCTION

In 1824, the Frenchman Arago discovered that the oscillations of a freely suspended magnetic needle
fade out much faster if there is a magnetic plate underneath them. Later experiments showed that when a copper plate rotates rapidly, a magnetic needle located above it begins to oscillate in the same direction.
An explanation for this was given by the Englishman Faraday
(1831). He proceeded from the fact that electric and magnetic fields are interconnected, and if around a conductor with
electric current produces a magnetic current, then the converse is also true: APPEARANCE
ELECTRIC CURRENT IN A CLOSED CONDUCTOR,
UNDER THE INFLUENCE OF A MAGNETIC FIELD.

Faraday conducted a series of experiments. To non-magnetic
1
the rod is wound with two pieces of copper pro- K
water. One(1) connected to Battery B WTOB
swarm (2) to the galvanometer G. At constant
current in wire 1, the galvanometer needle does not
G
deviates, and this means there is no current in wire 2. 2
When switch K was closed and opened, the galvanometer needle deviated slightly and quickly
returned to its original position, which showed
the appearance in circuit 2 of a short-term current called INDUCTION CURRENT. The direction of this
the current when opening and closing the key was opposite. It was unclear what was causing it
the occurrence of induction current: a change in the initial current or magnetic field.

If to the K₂ coil with a galvanometer G K₁ I
S
1
connect coil K₁ with battery B
B
creating a current I 1, then in K₂ there will be
N
current I 2. When removing the K₁ coil from
K₂ current I 2 arises, but is directed K₂ I
2
opposite.
G
Induction current occurs in the same way
if to a coil with a galvanometer
bring the magnet and move it along the coil.
The direction of the induction current depends on which end of the magnet was facing the coil, and on
whether he was approaching or moving away.
The reason for the appearance of induction current I 2 is
change in the magnetic field created by the coil
K₁ or magnet.

FARADAY'S LAW

ELECTROMAGNETIC INDUCTION

The phenomenon discovered by Faraday was called:
ELECTROMAGNETIC INDUCTION – occurrence
electromotive force in a conductor moving in
magnetic field, or in a closed conducting loop when its flux linkage changes. (due to
movement of the circuit in a magnetic field or changes
the field itself).
The appearance of an induction current in the circuit indicates
the presence in the circuit of an electromotive force (EMF), called electromagnetic force
induction (induction emf Ei).
The value of the induced current, and therefore the induced emf
determined only by the rate of change of magnetic flux.

FARADAY'S LAW OF ELECTROMAGNETIC INDUCTION

The EMF of electromagnetic induction in the circuit is numerically equal and opposite in sign to the rate of change
magnetic flux through a limited surface
this contour.
The law is universal Ei does not depend on the method of change
magnetic flux.
d
Ei
dt
BASIC LAW OF ELECTROMAGNETIC INDUCTION
The unit of Ei is V (volt).
Wb
T m 2
N m2
J
A B c
d
IN
dt
With
With
A
m
With
A
With
A
With

LENZ'S RULE

The “-” sign indicates that the increase in flow d dt 0
causes induced emf less than zero d dt 0 Ei 0
that is, the field of the induced current is directed towards the flow, and vice versa, d dt 0 Ei 0, that is, the direction of the flow and the induced current fields coincide.
The “-” sign is a mathematical expression LENZ’S RULES
– general rule to find the direction of the induction current.
The induced current in the circuit always has such a direction that the magnetic field it creates prevents the change in the magnetic flux that caused it
induced current.

To explain the occurrence of induced emf in stationary conductors, Maxwell suggested that any alternating magnetic field excites an electric field in the surrounding space, which is the cause of the appearance of induced current in
conductor.
The circulation of the strength vector of this field E B along any fixed contour L is
EMF of electromagnetic induction.
d
Ei E B dl
dt
L

FRAME ROTATION IN A MAGNETIC FIELD

Let the frame rotate uniformly ω
S
xia with angular velocityw const,
α
in a uniform magnetic field
IN
with induction B const.
Magnetic flux coupled to
frame at any time t will be equal to:
Bn S BS cos BS cos t
t – frame rotation angle at time t.
When the frame rotates, an induced emf Ei d dt BS sin t will arise in it, varying according to a harmonic law.
Ei max BS Ei Ei max sin t

If a frame rotates in a uniform magnetic field, then
a variable EMF appears in it, varying according to
harmonic law.
The phenomenon of electromagnetic induction was the basis
on the basis of which electric motors, generators and transformers were created.
GENERATORS – used to transform one
type of energy to another.
The simplest generator that converts mechanical
energy into electric field energy - the frame discussed above rotating in a uniform magnetic field. Mechanical conversion process
energy is convertible into electrical energy. On this principle
based on the action of electric motors that convert electrical energy V mechanical energy.

Eddy currents (FOUCAULD CURRENTS)

Induction current occurs not only in
thin wires, but also in massive solid conductors placed in an alternating magnetic field. These currents turn out to be closed in the thickness of the conductor and
called eddy or Foucault currents.
Foucault's currents obey Lenz's rule: their
the magnetic field is directed so that
counteract the change in magnetic flux inducing vortex
currents.
Eddy currents occur in wires carrying alternating current.
The direction of Foucault currents can be determined
dI
0
dt
I
dI
0
dt
I

pour according to Lenz's rule: if the primary current I increases (dI dt 0) then the Foucault currents are directed against the direction of I, and if it decreases (dI dt 0) then in the direction.
The direction of eddy currents such that they prevent a change in the primary current inside the conductor
and contribute to its change near the surface.
These are manifestations of the skin effect or surface effect.
Since high frequency currents practically flow in thin
surface layer, then wires are made for them
hollow.

LOOP INDUCTANCE SELF-INDUCTION MUTUAL INDUCTION TRANSFORMERS

INDUCTANCE. SELF-INDUCTION

An electric current flowing in a circuit creates an electromagnetic field around itself, the induction of which is proportional to the current. Therefore, linked to the circuit
magnetic flux is proportional to the current in the circuit.
LI
L – circuit inductance (induction coefficient)
When the current in the circuit changes, it will change
so is the magnetic flux attached to it, which means an EMF will be induced in the circuit.
The occurrence of induced emf in a conductive circuit,
when the current strength changes in it it is called -
SELF-INDUCTION.

The unit of inductance is Henry (H).
1 H – inductance of such a circuit, magnetic flux
the self-inductance of which at a current of 1 A is equal to 1 Wb.
For an infinitely long solenoid, the total magnetic flux (flux linkage) will be equal to:
N 2I
N 0
S
l
This means that the inductance of an infinitely long circuit is:
N 2S
L 0
l
The inductance of the solenoid depends on the number of turns N,
length l, solenoid area S and magnetic permeability of the substance from which the solenoid is made.

SELF-INDUCTION EMF

The inductance of the circuit depends in general only
from geometric shape, size and magnetic pro
worthlessness environment contour, and, you can
say that the inductance of a circuit is an analogue of the electrical capacitance of a solitary conductor.
Applying Faraday's law to self-induction (Ei d dt)
we get:
d
d
dL
dI
Es
LI L I
dt
dt
dt
dt
If the circuit is not deformed (L const), and the magnetic
the permeability of the environment does not change
hence:
dI
Es L
dt

The “-” sign shows that the presence of inductance in the circuit slows down the change in current in it.
If the current increases over time, then ES 0 and dI dt 0 then
there is a self-induction current directed towards the current caused by an external source and inhibits it
increase.
If over time the current decreases ES 0 and dI dt 0, then the induced current has the same direction as
decreasing current in the circuit and slows down its decrease.
The circuit, having a certain inductance, acquires electrical inertia: any change
The greater the inductance of the circuit, the more strongly the current is inhibited.

CURRENTS WHEN OPENING AND CLOSING THE CIRCUIT

For any change in current strength in a conductive circuit
self-induction emf occurs, as a result of which additional currents appear in the circuit called
EXTRACURRENTS OF SELF-INDUCTION. According to the rule
Lenz, they are always directed so as to prevent a change in the current in the circuit (opposite to the current from
R
E
TO
current source).
Consider a circuit having a source toL
ka with EMF E, resistance resistor R, inductor L. Under the influence of external EMF in the circuit
direct current I 0 E R flows.
At time t=0 the current source was turned off. The current through coil L will decrease. What will cause the appearance of self-inductive emf Es L dI dt obstructive

according to Lenz's rule of reduction
current At every moment of time
The current is determined by Ohm's law:
ES
dI
dI
R
I
IR L
dt
R
dt
I
L
I
I0
short circuit
opening
t
Integrating this expression over I (changing from I 0 to I) and
by t (changing from 0 to t) we get:
I
Rt
ln
I0
L
I I 0e
t
Current at time t after turning off the source.
L
– relaxation time constant (time during which
then the current decreases by a factor of e).
The greater the inductance of the circuit and the less resistance, the less, and therefore the slower the decrease

There is current in the circuit when it opens.
When the circuit is closed, in addition to the external EMF E,
Self-inductive emf Es L dI dt preventing the current from increasing. According to Ohm's law:
dI
IR E Es E - L
dt
du
dt
Let u IR E
u
At the moment of circuit closure, the current strength is I 0 and u E, which means integrating over u (from E to IR E) and over t (from 0 to t)
IR E t
we get
ln
E
t
I I 0 (1 e)
E
Current at time t after switching on. (I 0).
R

MUTUAL INDUCTION

Consider two fixed conesI1 1 I 2 2
tours 1 and 2 located close
from each other. Circuit 1 is leaking
the current I1 and the magnetic flux generated by this circuit are proportional to I1.
Let us denote by 21 that part of the magnetic flux that penetrates circuit 2. 21 L21 I1 (L21 is the proportionality coefficient).
If the current I1 changes, then Ei 2 is induced in circuit 2
EMF, which, according to Faraday's law, is equal and opposite in sign to the rate of change of magnetic
flow 21 created by the current in the first circuit and penetrating circuit 2.

d 21
dI1
Ei 2
L21
dt
dt
Similarly, when current flows in circuit 2, we obtain:
12 L12 I 2
d 12
dI 2
Ei1
L12
dt
dt
The phenomenon of the occurrence of EMF in one of the circuits, when
change in current strength in another is called
BY MUTUAL INDUCTION.
L12 and L21 – mutual inductance of the circuits, depend
on the geometric shape of the dimensions, the relative position of the contours and magnetic permeability
environment. The unit of measurement is Henry (H).
L12 L21
Experiments have shown that:

Let's calculate mutual inductance
l
two coils wound on a coil I
1
N2
pure toroidal core.
N1
S
Magnetic field induction created by the first coil, with the number of turns N1, current I 1 and
magnetic permeability of the core length l
N1 I 1
is equal to:
B 0
l
Magnetic flux through one turn of the second coil:
N1 I 1
2 BS 0
S
l
Total magnetic flux (flux linkage) through
secondary winding containing N 2 turns:
N1 N 2
N 2 2 0
I1 S
l

Since flux linkage is created by current I 1 then:
N1 N 2
L21 0
S
I1
l
If we calculate the magnetic flux created by coil 2 through coil 1, then for inductance L12 we similarly obtain the same value. Means
mutual inductance of two coils wound on
common toroidal core:
N1 N 2
L12 L21 0
S
I1
l

TRANSFORMERS

For the first time transformers were
R1
designed by Russian electricians E1 N1
N 2E2
technical technician P.N. Yablochkov
(1847-1894) and physicist I.F. Usagin (1855-1919).
The operating principle of transformers used for
increase or decrease AC voltage
current, is based on the phenomenon of mutual induction.
Let the primary and secondary coils (windings) having N1 and N2 turns, respectively, be mounted on a closed iron core. The ends of the first winding
attached to the source EDSE1, an alternating current I 1 arises in it, creating an alternating magnetic flux in the transformer core, practically

completely localized in the iron core,
which means it completely penetrates the turns of the secondary
windings A change in this flux causes the appearance of a mutual induction emf in the secondary winding,
and in the primary EMF of self-induction.
The current I 1 of the primary winding is determined using Ohm's law where R1 is the resistance of the primary winding.
d N1
E1
I1 R1
dt
The voltage drop I1 R1 across resistance R1 in rapidly varying fields is small compared to each
from EMF, and we can assume that:
d
E1 N1
dt

EMF of mutual induction arising in the secondary winding:
d(N)
d
E2
N 2
dt
dt
Comparing the values ​​of mutual EMF E2 and self-induction E1
2
we get:
N2
E2
E1
N1
E2 – EMF arising in the second winding, the “-” sign is
indicates that the EMF in the first and second windings are opposite in phase.
N2
– transformation ratio, shows speedN1
only once the EMF in the secondary winding is greater (less)
than in the primary one.

Neglecting energy losses (approximately 2%), and applying the law of conservation of energy, we can assume that
E2 I 2 E1 I1
Hence:
N2
1
N1
E2
I1 N 2
E1 I 2 N1
– step-up transformer increasing
alternating EMF and reducing current (applied
for transmitting electricity over long distances)
N2
1 – step-down transformer reducing
N1EMF and boosting current (used in electric welding, which requires high current at low voltage).




























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Abstract for the presentation

The presentation "Electromagnetic induction" describes Faraday's experience, the discovery of electromagnetic induction and the law governing it, the method of obtaining induction current, etc. The second half of the presentation contains a number of tasks and tasks that will help students prepare for the State Exam.

  • Faraday's experiment;
  • Magnetic flux;
  • Faraday's law of electromagnetic induction;
  • Lenz's rule;
  • Obtaining induction current.

    Format

    pptx (powerpoint)

    Number of slides

    Popova I.A.

    Audience

    Words

    Abstract

    Present

    Purpose

    • To conduct a lesson by a teacher

      To conduct a test / verification work

Slide 1

Slide 2

Target

Repetition of the basic concepts of kinematics, types of motion, graphs and formulas of kinematics in accordance with the GIA codifier and the plan for the demonstration version of the examination paper.

Slide 3

Discovery of the phenomenon of electromagnetic induction

  • The phenomenon of electromagnetic induction was discovered by the outstanding English physicist M. Faraday in 1831. It consists in the occurrence of an electric current in a closed conducting circuit when the magnetic flux penetrating the circuit changes over time.
  • Faraday Michael (22.09.1791–25.08.1867)
  • English physicist and chemist.

  • Slide 4

    Faraday's experiment

  • Slide 5

    The phenomenon of electromagnetic induction

    The phenomenon of electromagnetic induction consists in the occurrence of an electric current in a closed conducting circuit when the magnetic flux penetrating the circuit changes over time.

    Slide 6

    The phenomenon of electromagnetic induction

  • Slide 7

    Magnetic flux

    • The magnetic flux Φ through the area S of the circuit is the quantity
    • Φ = B S cos α
    • where B is the magnitude of the magnetic induction vector,
    • α – angle between the vector and the normal to the contour plane
    • The SI unit of magnetic flux is called weber (Wb)

  • Slide 8

    The phenomenon of electromagnetic induction

  • Slide 9

    Faraday's law of electromagnetic induction

    Lenz's rule:

    • When the magnetic flux changes in a conducting circuit, an induced emf Eind arises, equal to the rate of change of the magnetic flux through the surface bounded by the circuit, taken with a minus sign:
    • In this example, a ind< 0. Индукционный ток Iинд течет навстречу выбранному положительному направлению обхода контура.

  • Slide 10

    Dependence of induction current on the rate of change of magnetic flux

  • Slide 11

    Lenz's rule

    • I case
    • II case
    • III case
    • IV case

  • Slide 12

    Magnetic flux change

    A change in the magnetic flux penetrating a closed circuit can occur for two reasons:

    • The magnetic flux changes due to the movement of the circuit or its parts in a time-constant magnetic field.
    • Change in time of the magnetic field with a stationary circuit.

  • Slide 13

    Obtaining induced current

  • Slide 14

    Alternator

  • Slide 15

    The phenomenon of electromagnetic induction is observed in cases

    • movement of the magnet relative to the coil (or vice versa);
    • movement of the coils relative to each other;
    • changing the current strength in the circuit of the first coil (using a rheostat or closing and opening a switch);
    • rotation of the circuit in a magnetic field;
    • rotation of the magnet inside the circuit.

  • Slide 16

    Let's consider the tasks

    A selection of tasks on kinematics (from the tasks of the State Academy of Arts 2008-2010)

  • Slide 17

    Tasks

    When the south pole of the magnet is inserted into the coil, the ammeter records the occurrence of an induction current. What needs to be done to increase the strength of the induction current?

    • increase the magnet insertion speed
    • insert a magnet into the coil with the north pole
    • change the polarity of the ammeter connection
    • take an ammeter with a lower division value

  • Slide 18

    The coil is connected to a galvanometer. In which of the following cases does an electric current occur in it? A) An electromagnet is pushed into the coil. B) The coil contains an electromagnet.

    1. Only A.
    2. Only B.
    3. In both cases.
    4. In none of the above cases.

  • Slide 19

    Two identical coils A and B are each connected to its own galvanometer. A strip magnet is inserted into coil A, and the same strip magnet is removed from coil B. In which coils will the galvanometer detect the induced current?

    1. in none of the
    2. in both coils
    3. only in coil A
    4. only in reel

  • Slide 20

    Once the magnet falls through a stationary metal ring with the south pole down, the second time with the north pole down. Ring current

    1. occurs in both cases

  • Slide 21

    The current in the coil changes according to the graph in the figure. At what time intervals can not only a magnetic field, but also an electric field be detected near the end of the coil?

    1. From 0 to 2 s and from 5 to 7 s.
    2. Only from 0 to 2 s.
    3. Only from 2 to 5 s.
    4. At all specified time intervals.

  • Slide 22

    A magnet is pushed into the metal ring during the first two seconds, during the next two seconds the magnet is left motionless inside the ring, and during the next two seconds it is removed from the ring. At what time intervals does current flow in the coil?

    1. 0–6 s
    2. 0–2 s and 4–6 s
    3. 2–4 s
    4. only 0–2 s

  • Slide 23

    A permanent magnet is inserted into a closed aluminum ring on a thin long suspension (see figure). The first time - by the north pole, the second time - by the south pole. Wherein

    1. in both experiments the ring is repelled from the magnet
    2. in both experiments the ring is attracted to the magnet
    3. in the first experiment the ring is repelled from the magnet, in the second the ring is attracted to the magnet
    4. in the first experiment the ring is attracted to the magnet, in the second the ring is repelled from the magnet

  • Slide 24

    The magnet is removed from the ring as shown in the figure. Which magnet pole is closest to the ring?

    1. northern
    2. southern
    3. negative
    4. positive

  • Slide 25

    The figure shows a demonstration of an experiment to verify Lenz's rule. The experiment is carried out with a solid ring, not a cut one, because

    1. the solid ring is made of steel, and the cut ring is made of aluminum
    2. a vortex electric field does not arise in a solid ring, but in a cut ring it does
    3. An induced current occurs in a solid ring, but not in a cut ring.
    4. An induced emf occurs in a solid ring, but not in a cut ring.

  • Slide 26

    The figure shows two ways to rotate a frame in a uniform magnetic field. Current in frame

    1. occurs in both cases
    2. does not occur in any of the cases
    3. occurs only in the first case
    4. occurs only in the second case

  • Slide 27

    The figure shows the moment of a demonstration experiment to test Lenz's rule, when all objects are motionless. The south pole of the magnet is inside the solid metal ring, but does not touch it. The rocker arm with metal rings can rotate freely around the vertical support. When the magnet moves out of the ring, it will

    1. stay still
    2. move counterclockwise
    3. oscillate
    4. follow the magnet

  • Slide 28

    Literature

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    Abstract

    Physics teacher

    Belovo 2013

    Explanatory note

    Literature

    Peryshkin, A.V., Physics. 7th grade. Textbook for secondary schools / A. V. Peryshkin. - M.: Bustard, 2009. – 198 p.

    Peryshkin, A.V., Physics. 8th grade. Textbook for secondary schools / A. V. Peryshkin. - M.: Bustard, 2009. – 196 p.

    Municipal budgetary non-standard educational institution

    “Gymnasium No. 1 named after Tasirov G.Kh. City of Belovo"

    Electromagnetic induction. Faraday's experiments Preparation for the State Examination.

    Methodological manual (presentation)

    Physics teacher

    Belovo 2013

    Explanatory note

    Methodological manual (presentation) “Electromagnetic induction. Faraday's experiments. Preparation for the State Examination" was compiled in accordance with the requirements for the State Final Certification (SFA) in Physics 2010 and is intended to prepare secondary school graduates for the exam.

    The brevity and clarity of the presentation allows you to quickly and efficiently repeat the material covered when repeating a physics course in the 9th grade, as well as using examples of demo versions of the State Academic Examination in Physics from 2008-2010 to show the application of basic laws and formulas in versions of exam tasks at levels A and B.

    The manual can also be used for grades 10-11 when repeating relevant topics, which will help guide students for an elective exam in their final years.

    Note: the movie file exceeds the maximum upload size on the portal, and when compressed, playback quality suffers. Therefore, to insert video clips onto slides (recommendations are indicated in the presentation), download the film from the addresses indicated on the slides and insert them in the indicated places. When inserting, set “play automatically when showing slides”, on the “Options” tab, check the “Full screen” box

    Literature

    Zorin, N.I. GIA 2010. Physics. Training tasks: 9th grade / N.I. Zorin. – M.: Eksmo, 2010. – 112 p. – (State (final) certification (in a new form).

    Kabardin, O.F. Physics. 9th grade: collection test tasks for preparation for the final certification for the basic school course / O.F. Kabardin. – M.: Bustard, 2008. – 219 p.;

    Peryshkin, A.V., Physics. 7th grade. Textbook for secondary schools / A. V. Peryshkin. - M.: Bustard, 2009. – 198 p.

    Peryshkin, A.V., Physics. 8th grade. Textbook for secondary schools / A. V. Peryshkin. - M.: Bustard, 2009. – 196 p.

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