2nd year junior high school students, physics problems, 2nd year physics problems

In 1 circuit, the resistance changes, the total voltage does not change, the current becomes the series circuit knowledge, the current is equal everywhere, if the resistance becomes larger, the current should become smaller.

First of all, you need to understand that resistance is an intrinsic property of electrical appliances, and once it is determined, resistance does not change with the voltage or current applied by the outside world.

Ohm's law actually describes the relationship between voltage and current when the resistance is determined, and its variants are used for physical calculations.

In the series circuit, because it is connected in series, the current in the circuit is equal everywhere, according to the formula U=IR, R becomes larger, if i is required to be constant, then only the voltage u increases to ensure that i is constant; And if r does not change, and the applied voltage u does not change, then i must decrease.

The current flowing through different electrical appliances in the series circuit is the same, according to U=IR, the greater the resistance of the electrical appliances, the greater the voltage at both ends, and if the resistance changes in a circuit, such as increasing, when the power supply voltage remains unchanged, the current must decrease, regardless of series or parallel.

Pay attention to the wording of these two statements, and you will understand that you are not talking about the same issue.

I just want to say that you can be the power supply voltage, if it is the power supply voltage must not change, if it is a change in the voltage at both ends of the resistor must be increased, are you confused about this?

The coefficient of judgment method requires two quantities to be known;

Both sides of the equation are balanced, and any problem can be solved;

i does not change, r becomes larger, and the left side of the equation must increase to balance, understand?

It depends on what the situation is, what his topic will say, who is the variable and who is the quantitative.

The formula can be changed, and the situation is treated on a case-by-case basis.

It depends on what the situation is, the series circuit is divided into voltages, the same current, the voltage with large resistance is large, and the current is unchanged.

This is uncertain, depending on whether it is connected in series or in parallel, the current flowing through each resistor in the series circuit is the same, but the voltage at both ends of each resistor is not necessarily the same, the voltage of each parallel resistor in the parallel circuit is the same, but the current flowing through each parallel resistor is not necessarily the same, when you change one resistor, the other resistors you and i will also change.

In a series circuit, if R1 and R2 are connected in series, if the power supply voltage is unchanged, the resistance R1 becomes larger, the current in the circuit becomes smaller, and the voltage at both ends of the resistor R2 becomes smaller, because the power supply voltage does not change, the voltage at both ends of R1 becomes larger.

The work done on the goods w=f*s=720*10=7200j The mechanical efficiency of the second pulley block is 60%, so the total work done by this person is multiplied by 60% to be 7200J, so the work done by this person is 7200 divided by 60%, which is 12000J

If it is pulled at a constant speed, it is: (720*10) 60%.

Accelerated pull junior high school does not require mastery.