Special Topic on Calculation of Electrical Power in Physics in the Second Year of Junior High School

1 pz220-100w bright.

2 pz220-40w bright.

When they are connected in parallel, they all emit light normally, and the power of 100W is large, so it is brighter.

When connected in series, the currents are equal. The resistance with small power is greater, and the voltage applied to both ends of it is greater, so the power consumed is large, and it is brighter, which depends on the actual power.

2: The voltage of the power supply is first required, the square of P1 divided by R1 = 10 times the root number 2

When connected in parallel, the power supply voltage remains unchanged, and the voltage added to each resistor is the same, and the power is calculated according to the relationship between power and resistance and voltage, and the power = the square resistance of the voltage.

The power of R1 is 100W

The R2 has a power of 25W

3: The voltage can be calculated in the circuit in parallel, and the square of the voltage is equal to the power multiplied by the resistance, so the voltage is 6V

1.One bulb labeled PZ220-40 and one bulb labeled PZ220-100, if; (1) Connect them in parallel on a 220V power supply and ask which light is brighter? (2) Put them in series on a 220V power supply, which light is brighter?

1 pz220-100w bright.

2 pz220-40w bright.

1) Of course, it is the second one, etc., the lamp with the same rated voltage, the higher the actual power, the brighter the lamp.

Electrical power refers to the amount of electrical energy generated by a generator per unit of time flowing through a circuit. The formula for electrical power: p=ui, p=i r, p=u r, p w t.

P (electrical power), U (voltage), I (current), W (electrical work), R (resistance), T (time).

1.The electrical power is equal to the voltage multiplied by the current p=ui.

2.The electrical power is equal to the square of the current multiplied by the resistance p=i r (pure resistive circuit).

3.The electrical power is equal to the square of the voltage divided by the resistance p=u r.

4.The electrical power is equal to the electrical work divided by the time p w t.

Electrical power refers to the amount of electrical energy generated by a generator per unit of time flowing through a circuit. Its SI unit is watts. When an electric current is passed through a circuit, it can convert energy into mechanical energy, or generate heat.

There are many types of electrical devices that use electrical power, such as heat generation (electric heaters), light (light bulbs), kinetic energy (electric motors), sound (speakers), or chemical changes (electroplating). Electrical power can be generated by generators, chemical reactions (batteries), solar energy (solar cells), or converted into chemical energy and stored in batteries.

Series connection: The total work done by the current is equal to the sum of the work done by the electrical current of each part.

The work done by the current through each resistance is directly proportional to its resistance.

Parallel: The total work done by the current is equal to the sum of the work done by the current of the electrical appliances of each part.

The work done by the current through each resistor is inversely proportional to its resistance.

(1) In the process of going from A to B, the voltage of the bulb gradually increases, and the current gradually increases. When it reaches point B, the bulb voltage is 12V and the current is 2A

So p = ui = 12x2 = 24 (w).

2) r total = u i = 12 1 = 12 ( ).

R lamp = U lamp i = 3 1 = 3 ( ).

r = r total - r lamp = 12 - 3 = 9 ( ).

3）i=p/u=

p slip = i i r slip =

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