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Download a presentation on the power of electric current. Electrical engineering and electronics Linear DC circuits. The end result will be the cost

Lesson topic:


Lesson topic:

Work and power electric current


1. What letter is used to denote electrical voltage?

  • 1) I 2) U 3) R 4) q

2. What is the unit of measure for electrical resistance called?

  • 1) Joule 2) Ampere 3) Ohm 4) Volt

3. What letter is used to denote the strength of the current?

  • 1) A 2) I 3) V 4) R

4. Which of the following values ​​is the same for all series-connected conductors?

  • 1) voltage 2) current 3) resistance 4) charge

5.Sila current in the conductor:

  • 1) is directly proportional to the voltage at the ends of the conductor and its resistance
  • 2) is inversely proportional to the voltage at the ends of the conductor and its resistance
  • 3) is directly proportional to the voltage at the ends of the conductor and inversely proportional to its resistance
  • 4) is directly proportional to the resistance of the conductor and inversely proportional to its resistance.

  • 1. 2)
  • 2. 3)
  • 3. 2)
  • 4. 2)
  • 5. 3)

Work of electric current

To determine the work of an electric current in any section of the circuit, it is necessary to multiply the voltage at the ends of this section of the circuit by electric charge passing through it.

A=U*q

A - Work,

U - Voltage,

q - Electric charge.


The work of an electric current is proportional to the strength of the current, voltage and time of passage of the current.

A=I*U*t

A - Electric current work,

I - Current strength,

U - Voltage,

t - Current passing time



Work of electric current

Unit of Work: Joule (J)

1 Joule = 1 Volt * 1 Amp * 1 second

1 J = 1 V * 1A * 1s


Units of work in multiples of the Joule: hectojoule, kilojoule, megajoule.

Express in Joules the work equal to


Instruments needed to measure the work of the current in the circuit:

Voltmeter

Ammeter


Power

Power is numerically equal to the work done per unit time.

P - Power


Power

Power unit: Watt (W)

1 Watt = 1 Volt * 1 Amp

1W = 1V * 1A


Units of power in multiples of watts: hectowatt, kilowatt, megawatt.

Express in watts the power equal to:



How much work is done by the electric current in light bulb in 3 minutes. Calculate the power of the electric current.



Name

Letter designation

Unit

Electric charge

Basic Formula

Current strength

Definition

Voltage

Resistance

Work of electric current

Power


Reflection

Continue the sentence:

  • Today in class I learned...
  • Now I can …
  • It was interesting…
  • The knowledge gained in today's lesson will be useful ...

Physics lesson in 8th grade.

, teacher of physics, MOBU "Nikitinskaya secondary school"

Theme: M electric current power.

Lesson type:combined.

Lesson Objectives:to reveal the concept of the power of an electric current, to find out on what factors the power of an electric current depends, to reveal methods for determining power.

Tasks:

Educational:

Educational:

    to consolidate the already existing knowledge on the topic "Electric current".

    get to know the concepts

    continue the formation of the ability to explain the processes in the electrical circuit.

    formation of communicative qualities, culture of communication

    formation of interest in the subject being studied

    stimulation of curiosity, activity in the lesson

    working capacity development

Developing:

    development of cognitive interest

    development of intellectual abilities

    development of skills to highlight the main thing in the studied material

    development of skills to generalize the studied facts and concepts

Forms of work:frontal, work in small groups, work in pairs, individual.

Means of education:

Textbook "Physics 8" A.V. Peryshkin

Collection of problems in physics for grades 7-9, A.V. Peryshkin,

Handouts (test sheets, practical tasks).

Sources of electric current.

Ammeters.

Voltmeters.

Electric light bulbs.

Connecting wires.

Presentation "Power of electric current".

Computer.

Illustrations on the topic.

Lesson plan:

Organizing time.

Express survey

staging learning objectives

Joint study of the problem

Designing a new mode of action.

Transition to the stage of solving particular problems

Control at the end stage learning topic

Homework.

Pedagogical technologies and teaching methods: ICT technology, research, problem-based teaching methods, elements of student-centered learning, differentiated learning

stage number

The work of the teacher.

Student work.

Notes in a notebook.

Slides used.

Time.

Greetings.

Safety briefing

slide 1.

2 minutes

Express survey:

slide 2

2 minutes

What is electric current?

An electric current is a directed (ordered) movement of charged particles.

Conditions for the existence of an electric current.

The presence of charged particles and electric fields

Components of an electrical circuit.

Current source, consumer, key, connecting wires

What particles generate electric current in metals?

Current in metals is generated by electrons

What are the quantities of electric current?

Electrical voltage and current

Write the formula for current.

slide 3

2 minutes

What is taken as a unit

current strength?

Current strength is measured in amperes

The formula for electrical voltage.

What is the unit of voltage?

Voltage is measured in volts

What is the name of a device for measuring current? Voltages?

Ammeter, voltmeter

How is an ammeter, voltmeter connected to a circuit?

The ammeter is connected in series, observing the polarity.

The voltmeter is connected in parallel, observing the polarity

Read electrical circuit

The circuit consists of a series-connected current source, a resistor, a key, a voltmeter is connected in parallel to the resistor.

slide 4.

2 minutes

Show the direction of the current in the circuit

Find the fault in the circuit

no key

slide 6

1 min

Assemble the electric circuit

Slide 7

2 minutes

Draw a circuit diagram

Slide 8

2 minutes

Group work. Task: look at the light bulbs. If included in the circuit, will all the bulbs burn equally brightly.

No, bulbs have different wattages.

The work of the current shows how much work the electric field does.

Slide 9

2 minutes

What is the topic of the lesson?

Electric current power.

Electric current power.

slide 10.

2 minutes

What are the objectives of the lesson:

The physical quantity is studied according to the plan:

  1. Definition of quantity.

    Physical formula

    Units.

    Methods for measuring a quantity.

    What quantities connects.

2 minutes

Now let's remember from the 7th grade physics course, what is power?

Power is physical quantity, which shows how fast the work is done. Power is equal to the ratio of work to the time for which this work is done.

Power is equal to the ratio of work to the time for which this work is done.

3 min

mechanical power, which was mentioned in the 7th grade physics course, is denoted by the letter N , and we will denote the power of the electric current by the letter P. The units of power are watts.

[R] = W

Formula derivation

3 min

Power units

1W=1A*1V

1W=1A*1V

1 min

Historical reference about the scientist

James Watt
(James Watt )
(January 19, 1736 -
August 19, 1819) - Scottish mechanical inventor, creator of the universal steam engine. The unit of power, the Watt, is named after him, and Heriot-Watt University in Edinburgh.

Slide 11

2 minutes

Assignment to students:
express the power in watts

4g W=

62kW=

0.8 MW =

50 gW=

8.6 kV=

0.09 MW =

4g W= 400W

62k W = 62,000 W

0.8 MW = 800,000 W

50 gW= 5000 W

8.6 kV= 8 600 W

0.09 MW = 90,000 W

slide 12

3 min

What instrument should be used to measure

Group work:

Wattmeter

Ammeter, voltmeter

slide 14, 15

2 minutes

We do laboratory work.

Filling out forms for laboratory work

slide 16

6 min

Additional tasks:

1. Determine the current power in the conductor if the current strength is 0.5 A and the voltage is 4 V.

2. What should be the voltage in the circuit section if the power of the device is 0.66 kW at a current of 3 A.

3. The power of the electric iron is 6GW. Calculate the work done in 5 minutes.

2 W

220 V

180000 J

What are the units of measure for power, current, voltage?

What is the relationship between these units?

current work?

1. watt, amp, volt

2. 1 W = 1 A 1V

3. Ammeter, voltmeter.

Wattmeter

1 W = 1 A 1V

2 minutes

Summary of the lesson. Reflection.

2 minutes

Homework, necessary comments.

Recording homework in diaries.

Creative level: (website "cool physics")

1. Studies about scientists - choose discoveries in the field of electricity

Exercise 25 (1 task)

Additional tasks:

Slide 17

2 minutes

Used Books:

Peryshkin A.V. textbook "Physics 8"

Lukashk "Collection of problems in physics grades 7 - 9", Moscow, "Drofa", 2008

V.A. Orlov "Thematic tests in physics grades 7 - 8", Moscow, "Verbum - M", 2001

G.N. Stepanova, A.P. Stepanov "Collection of questions and tasks in physics grades 5 - 9", St. Petersburg, "Valery SPD", 2001

1 slide

2 slide

WORK OF ELECTRIC CURRENT The work of electric current shows how much work has been done electric field when moving charges along a conductor. The work of an electric current is equal to the product of the current strength and the voltage and the time the current flows in the circuit. The unit of measurement of the work of electric current in the SI system: [ A ] \u003d 1 J \u003d 1A B c

3 slide

POWER OF ELECTRIC CURRENT The power of electric current shows the work done by the current per unit of time and is equal to the ratio of the work done to the time during which this work was done. (power in mechanics is usually denoted by the letter N, in electrical engineering - by the letter P) since A \u003d IUt, the power of the electric current is: The unit of power of the electric current in the SI system: [P] \u003d 1 W (watt) \u003d 1 A. B

4 slide

LEARN, GO! When calculating the work of an electric current, an off-system multiple unit of electric current work is often used: 1 kWh (kilowatt-hour). 1 kWh = ............. W.s = 3,600,000 J which show the work of an electric current completed over a certain period of time when various household electrical appliances. These meters show the work of electric current (electricity consumption) in "kWh". 1 kWh of energy allows you to smelt 20 tons of pig iron

5 slide

WOW, INTERESTING At one time, J. Watt proposed such a unit as "horsepower" as a unit of power. This unit of measurement has survived to this day. But in England in 1882, the British Association of Engineers decided to assign the name of J. Watt to the unit of power. Now the name of James Watt can be read on any light bulb. This was the first case in the history of technology of assigning own name unit of measure. From this case, the tradition of assigning proper names to units of measurement began.

6 slide

They say that ... one of Watt's steam engines was bought by a brewer to replace the horse that powered the water pump. When choosing required power of the steam engine, the brewer defined the horse's labor force as eight hours of non-stop work until the horse was completely exhausted. The calculation showed that every second the horse lifted 75 kg of water to a height of 1 meter, which was taken as a unit of power of 1 horsepower.

7 slide

EVERYONE RUN TO THE TASKS! Two electric lamps, whose power is 40 and 100 W, are designed for the same voltage. Compare the filament resistances of both lamps. The room is lit with 40 electric lamps from a flashlight, connected in series and fed from the city network. After one lamp burned out, the remaining 39 were again connected in series and plugged into the network. When was the room brighter: with 40 or 39 lights? Connected in series copper and iron wires of the same length and section are connected to the battery. Which one will stand out large quantity heat for same time?

8 slide

Solve the problem In a circuit with a voltage of 125 V, an electric lamp is turned on, the current in which is 0.4 A. Find the current power in the lamp. (Calculate the work of the current in 10 minutes)