"How fast electric current does work" Current work and electric power PPT courseware 2

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"How fast electric current does work" Current work and electric power PPT courseware 2

Knowledge review:

What is electric power? What are its two units? What's the conversion relationship?

The work done by electric current is called electrical work;

The units are joules and degrees;

1 degree = 1 kilowatt hour

1 degree = 3.6×106 joules

When current passes through the motor of an electric fan and is powered on for half an hour, the current does 72,000J of work; when current passes through the motor of a washing machine and is powered on for 2 minutes, the current does 12,000J.

Which motor does more work due to the current flowing through it?

(More work done by fan motor)

Which motor does work faster when current passes through it?

1. What is electrical power?

1. Electric power is a physical quantity that expresses the speed of work done by electric current.

2. Definition: The work done by electric current in unit time.

3. Formula: P=W/t

P represents electrical power. Unit: watt, referred to as watt (w)

W represents electrical power, unit: Joule, symbol: J

t represents time, unit: second, symbol: s

4. Another unit of electrical power is kilowatt. Symbol: kw.

The relationship between kW and W is: 1 kw=10³w

2. Scientific inquiry:

1. Ask questions:

What factors are related to electrical power?

2. Assumptions and conjectures:

From P= W/t, W=UIt, we can get P= IU

Conjecture: Electric power is related to the voltage across the circuit and the current in the circuit.

3. Make plans and design experiments::

(1) What physical quantities need to be measured?

U.I.

(2) Design experimental circuit diagram:

(3) Select experimental equipment and connect the circuit:

Precautions:

1. When connecting the circuit, the switch should be in the "off" position.

2. When connecting the circuit, the sliding blade of the sliding rheostat should be at the maximum resistance value.

4. Experimental conclusion:

Electric power P is proportional to the voltage U across the electrical appliance and the current I in the circuit.

3. Calculation formula of electric power:

P=IU

Among them: P represents electrical power, unit: Watt (W);

I represents current, unit: ampere (A).

U represents voltage, unit: volt (V);

Rated voltage and rated power:

The voltage when the electrical appliance is working normally is called the rated voltage.

The power of an electrical appliance at rated voltage is called rated power.

The relationship between actual power and rated power:

When U real = U amount, P real = P amount, the electrical appliance works normally;

When U is in real-time, P is in real-time, and the electrical appliance cannot work normally;

When U reaches the U limit and P reaches the P limit, the electrical appliances are easily burned.

Class exercises

A 1.4 ohm resistor connected to an 8 volt circuit consumes ____ watts.

2. There is a small light bulb marked "8V, 2W". If it is connected to a 12-volt power supply, a resistor with a resistance value of ____ ohms must be ______ connected to make the small light bulb glow normally. At this time, the electrical power consumed by this resistor is ____ watts.

3. A light bulb marked "220V, 40W" has a rated voltage of _____V, a rated power of _____W, a rated current of _____A, and a resistance of ______Ω. If this light bulb is connected to both ends of the 110V power supply, its resistance is ______ Ω, the voltage across the light bulb is _____V, the current flowing through it is _______A, and its actual power is _____W.

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"How fast electric current does work" Current work and electric power PPT courseware 3:

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"How fast or slow the current does work" Current work and electric power PPT courseware:

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Update Time: 2024-07-30

This template belongs to Physics courseware Shanghai Science Edition Ninth Grade Physics industry PPT template

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