Physics Ohm s law calculation problems and electric power calculation problems

Definition formula for electrical power:

p=w/t。

Derivation formula: w=iut, p=w t=uit t=ui.

And according to Doomming Ohm's law: i=u r

There are: u=ir, p=ui=iti=i and p=ui=u u r=u r.

Answer: n-electric power u-voltage r-resistance i-current.

n=u squared r n=i squared r

Ohm's Law:

1.In the circuit where the two lamps L1 and L2 are connected in parallel to a circuit with a voltage of 12V, the trunk current is and the current through L1 is is, what is the resistance of the two lamps?

2.When the voltage at both ends of a resistor increases from 2V to yes, and the current through the resistor increases, what is the resistance value of the resistor?

3.The total resistance of the two resistors in series is 20 ohms, and the total resistance after parallel connection is in ohms, so what are the resistance values of these two resistors?

4.When a voltage of 6V is applied to both ends of a resistor. The current that passes through it is 600mA. If voltage is applied to both ends of this resistor, what is its resistance?

5.What is the ratio of R1 to R2 resistance when the voltage applied to the two fixed-value resistors R1 and R2 is 2:1, and the ratio of the current passing through them is 4:3?

6.The resistance r is 18 ohms, so that the voltage applied to both ends of it is 1 3 of the total voltage, a ( ) ohm resistor should be connected in series; To make the current passing through it 1 4 of the total current, it should be given a ( ) ohm resistor in parallel.

7.If the total resistance of R1 and R2 (R1>R2) in parallel is R, the current through R1 is I1, and the current through R2 is I2. then r( )r2,,i1( )i2.

8.Give you a fixed value resistor marked with "10 ohms" and a sliding rheostat marked with "30 ohms", under the premise of ensuring the safety of all circuits, if the circuit is connected in series, the current allowed to pass through the circuit is ( ) ampere, and the maximum voltage allowed to be added at both ends of them is ( ) v.

9.If two different voltages of U1 = 4V and U2 = 6V are added to both ends of R, what is the ratio of the current passing through the conductor twice?

10.If two resistors of 4 ohms and 6 ohms are connected in series on a power supply with constant voltage, the current in the circuit is, if they are connected in parallel in the same circuit, what should be the dry circuit current?

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We already know that lung capacity is the volume of air exhaled by a person who does the maximum inhalation followed by the maximum exhalation, in milliliters (ml). Lung capacity is one of the important indicators of physical function, which has a great impact on the growth of adolescents and their future health.

We need to pay attention to increasing our lung capacity. Figure 2 shows a practical method for measuring spirometry, where a is an open, thin-walled cylinder that is upside down in water, and the air in it is exhausted before the measurement (i.e., the cylinder is filled with water before the measurement). During the measurement, the person inhales enough air, and then exhales the air as much as possible through B, and the exhaled air enters A through the catheter to make A float.

The mass of the cylinder is measured, the cross-sectional area is s, the height of the bottom of the cylinder is h, and the atmospheric pressure is p0

1. The volume of gas in the cylinder at this time.

2 The pressure of the gas in the cylinder at this time.

3 "Spirometry body mass index" is an important respiratory function index of the human body, which mainly reflects the correlation between lung capacity and body weight through the ratio of lung capacity to body weight, and is used to conduct objective quantitative comparative analysis of individuals and groups of different ages and genders.

For example, the body mass index standard for male students in the third grade of junior high school in China: 67 or above is excellent; 50 66 is good; 33 49 is passing; 32 or below is a failure.

If Xiaoqiang, who weighs 60kg, measures his spirometry with the spirometer above, and measures h=18cm, the mass of tube A is known.

For 200g and a cross-sectional area of 200cm2, please calculate what is his lung capacity body mass index?

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You're a student of Sindu, and I'm looking for a question, and I feel the same way.

Electrical power1 Definition: The work done by an electric current per unit of time.

2 Physical Meaning: Representation.

Electric current does work. Fast and slow physical quantities. The brightness of the bulb depends on the actual power of the bulb.

3 Electrical power calculation formula: p=ui=w t (applicable to all circuits) for pure resistive circuits.

It can be derived: p=i2r=u2 r

Series circuits. The commonly used formula is: p=i2r

p1：p2：p3：…pn=r1：r2：r3：…: rn parallel circuit.

The commonly used formula is: p=u2 r

p1：p2=r2：r1

Regardless of the electrical appliances.

Series or parallel. Calculate the total power.

The common formula is p=p1+p2+....pn

4 Units: SI units.

Watts (w) commonly used units.

Kilowatts (kW).

6: When k

Disconnect, k, k

When closed, the circuit is connected in parallel, U total = U1 = U2 = 12V, which can be obtained from the closed circuit Gynm's law: i1 = U R1 = 12 6 = 2A

i2=u r2=12 8=dangk

Closed, k, k

When disconnected, r1, r2 are connected in series, r total = r1 + r2 = 6 + 8 = 14 ohms.

From the law of closed circuits, it can be obtained: i total = u r = 12 14 = 6 7a so, u = ir1 = 6 7 times 6 = 36 7vu2 = ir2 = 6 7 times 8 = 48 7v