A question about Ohm s law in physics in the second year of junior high school

When the sliding vane is at the top, the resistance value is zero, the voltage on r is AB, and the voltage between them is 10V (maximum).

The current is 10 30 = maximum).

When the slide is at the bottom, that is, the resistance value is the maximum is 10, and the constant resistance current is the entire circuit 10 (10+30)=minimum).

resistance r voltage is minimal).

Voltage and current 4:3

When the sliding blade reaches the top, the resistance value of the rheostat in the access circuit is 0, the voltage of the voltmeter is equal to the power supply voltage 10V, and the current of the fixed value resistance is the maximum 10V 30; When the sliding vane reaches the lowest end, the resistance value of the rheostat in the access circuit is the largest, and the voltage of the total voltage 10V * [10 (10 +30 )] = is separated, so the voltage is expressed at a minimum of 10V (10 +30 )

So the answer is to 10v 4:3

The sum of the voltage of the custom resistor R and the voltage of the sliding rheostat is equal to the power supply voltage, that is, the minimum resistance of the sliding rheostat is the maximum V.

So when r slip = 0, u = 10v i = 10 30 = r slip = 10 i = 10 (10 + 30) =

U = Ratio: 4:3

Physics: Follow the current, grasp the resistor's hand...

The voltmeter can vary from 10 V. The ratio of the maximum current to the minimum current on a fixed-value resistor is 4:3.

Just consider the two extremes, you can have two cases when the variable resistance is 0 ohms and 10 ohms, the total resistance at 0 ohms is the smallest, the current is the maximum, and the voltage of the constant resistance is also the largest, and the voltage of the constant resistance is also the largest at 10 ohms.

Sliding rheostat slides to maximum, total resistance 40, current, voltmeter, slides to minimum, resistance 30, current, voltage 10v. So the ratio of voltage from 10V to current is 4:3

Original question: 1. When the voltage at both ends of a certain section of conductor is 3V, the current passing through it is 06a, then the resistance of the conductor is ?

2. When the voltage at both ends of the conductor is reduced by half, the resistance is ?

3. When the circuit is disconnected, the current value in this section of conductor is a? The resistance is ?

1. When the voltage at both ends of a certain conductor is 3V, the current passing through it is 0 6a

Find: The resistance of the conductor.

Solution: According to the meaning of the question, it can be obtained: r=u a

Answer: When the voltage at both ends of a certain section of conductor is 3V, the current passing through it is 06a, then the resistance of the conductor is 5.

2. A: Although the voltage at both ends of the conductor is reduced by half, it is the resistance of the same conductor, so when the voltage at both ends of the conductor is reduced by half, the resistance is 5.

3. A: When the circuit is disconnected, the current value in this conductor is 0A, and the resistance is 5. Because resistance is a property of the conductor itself and does not change with changes in voltage or current; Rather, it is determined by the material, length, and cross-sectional area.

1》When the voltage at both ends of a certain section of conductor is 3V, the current passing through it is 06a, then the resistance of the conductor is ?

r＝u/i＝3/

2》When the voltage at both ends of the conductor is reduced by half (3 2, the current through it is still 06a), the resistor is:

r＝u/i＝

3》When the circuit is disconnected, the current value in this section of conductor is zero (no current passes); The resistance value does not change (the wire resistance is fixed).

The resistance of the conductor r=u i=3v

When the voltage at both ends of the conductor is reduced by half, the current is reduced by half, and the resistance is still 5, r=u i=

When the circuit is disconnected, the current value in this section of conductor is 0A and the resistance is 5.

Because resistance is a property of the conductor itself, its magnitude is determined by the material, length and cross-sectional area of the conductor itself, and is also affected by temperature. It has nothing to do with the voltage at both ends of the conductor and the current passing through.

c. Unclear can be asked.

This is a series circuit, and the voltmeter measures the voltage of the sliding rheostat.

When the left shift, the resistance of the sliding rheostat becomes larger, the total resistance of the series circuit becomes larger (R total = R slip + R lamp), and the total current becomes smaller (i = u total (r slip + r lamp) - the indicator of a becomes smaller.

If the resistance of the lamp does not change, the voltage of the lamp will become smaller (U lamp = IR lamp), the voltage of the sliding rheostat will become larger (U slip = u total - u lamp), and the indicator of -V will become larger.

So choose C

Select C1) It can be seen from the figure that the rheostat is connected to the lamp in series, when P moves to the left, the resistance of the rheostat to the circuit becomes larger, so that the total resistance in the circuit becomes larger, and the power supply voltage remains unchanged, and the current becomes smaller from i=u r, so the current representation becomes smaller;

2) Because the rheostat is connected in series with the lamp, the current in the circuit is constant, and when p moves to the left, the resistance of the rheostat to the circuit becomes larger, and the voltage representation will become larger because of the u=u r.

The answer is selected: c When the sliding blade moves to the left, the resistance of the sliding rheostat increases, this circuit is a series circuit, then the total resistance of the circuit increases, according to i = u r, r increases, u does not change, then i decreases, so the current representation number becomes smaller, and because i decreases, the resistance of the bulb does not change, then according to: u = ir, it can be known:

The voltage at both ends of the bulb decreases, and the sum of the voltages of the series circuit and each appliance is equal to the power supply voltage, so the voltage at both ends of R increases, so the answer is C.

Of course, it's c, the rheostat slides to the left, the resistance becomes larger, and the current becomes smaller.

Hello! This question is selected D.

The way to do this circuit diagram reading problem is very simple. (junior high school stage) cover the voltmeter first, because the resistance of the voltmeter is very large (thousands to tens of thousands), which can be regarded as an open circuit (as long as the other resistors are small). In this way, it can be found that the entire sliding rheostat is actually connected to the circuit, and r is unchanged.

Therefore, the indication of the ammeter i=u r does not change. Now let's look at the voltmeter. The voltmeter measures the resistance of the resistor to the left of the sliding rheostat.

According to Ohm's law, i in a circuit is equal, so the ratio of the voltage on the resistor is equal to the ratio of the resistance, that is, the greater the resistance, the greater the distributed voltage, and the number of the voltmeter increases.

D, of course. Analysis: This slip resistance is not when the slip resistance is in use, the circuit is connected to two lower binding posts, that is, it has always been the maximum resistance, the slide p is only connected to one end of the voltmeter, in fact, the slip resistance is divided into two sections to measure the voltage division of the left section.

d moves to the right and the voltage increases and the loop does not change, so the current does not change.

First of all, we must understand the influencing factors of resistance, voltage, and current. Resistance is affected by its length, material, cross-sectional area, and sometimes temperature. For example, with a road, there is an obstacle in the road, which hinders people when they pass by, and also uses an obstruction when people do not pass, but it does not show it.

In the same way, it is known that voltage and current can find resistance, but when the voltage changes, the resistance does not change, and the current changes. All resistor magnitudes are independent of current and voltage.

The answer is: 12 ohms, amps 12 ohms 0 12 ohms.

Ohm's law: voltage current x resistance, i.e. u = ir

Resistance is an intrinsic property of the wire, which does not change due to the change of voltage or current when the voltage is 6 and the resistance is 6 when the current is 6, and the resistance remains the same forever when the voltage is 18 and the current i 18 12

When the voltage is 0, the current i 0 12 0 and the resistance is unchanged at 12 ohms.

r=u i=6v ohm.

If the temperature is constant, the resistance is unchanged = 12 ohms, then i = u r = 18 V 12 ohms =

From i=u r, we can see that u=0 i=0 resistance is still constant.

Ohm's law deformation formula gives r=u i=6v

The resistance is constant, and Ohm's law formulas that i=u r=18v 12 = resistance is constant, r=12

There is no current without voltage, i=0a resistance is always constant, r=12

The resistance of this wire is now also calculated by you? It depends on the length of the wire, the cross-sectional area, the temperature, and the material!

Not really!