The resistance value of the resistance to be measured in the physical circuit is small on the outsid

Small external bias: when measuring the resistance value of the small resistance (when rx>>ra) the circuit is connected to the ammeter external method, the voltmeter shunts at this time, resulting in system error, the current representation number is larger than the actual current through the resistor, and the actual voltage value is the voltage representation number, so the measured resistance value is small;

Large external bias: When measuring the resistance value of a large resistor (when RX "I hope it can help you!")

Small external bias: If the resistance to be measured is very small, because the ammeter has internal resistance, the voltage shared by the internal connection cannot be ignored, so it should be externally connected. The current measured by the external ammeter is the total current, including the current through the voltmeter, so I is large, resulting in R is small.

Large internal bias: If the resistance to be measured is very large, because the voltmeter has internal resistance, the current through the voltmeter will be very large and cannot be ignored if it is externally connected, so it is connected internally. The voltage measured by the internal voltmeter is the total voltage, including the voltage at both ends of the ammeter, so you are larger, resulting in r being larger.

This formula is used to determine the difference between the internal and external connection method of the ammeter and the result of measuring the resistance value and the actual resistance value.

Small outside, that is, the resistance to be measured is close to the internal resistance of the ammeter, the ammeter is external, small means that the last measured resistance is small, large inside, it means that the resistance to be measured is larger than the internal resistance of the ammeter, the ammeter is connected, and the large is said that the final measured resistance is larger. Hope.

The full name of the internal method is the ammeter.

In the internal method, the actual measured result is the result of "resistance and ammeter internal resistance in series", so the result is large.

In order to prevent the influence of the internal resistance of the ammeter, it is generally used to measure large resistance.

The full name of the external method is the external method of ammeter, and the actual measured result is "resistance and voltmeter."

parallel", so the result is smaller than it actually is.

In order to prevent the influence of the internal resistance of the voltmeter, it is generally used to measure small resistance.

The small resistance is connected by the external method, and the measured value is smaller than the real value, and the value measured by the internal resistance is larger than the real value.

It is mainly caused by the partial voltage of the ammeter.

It should be related to the connection method of the ammeter and voltmeter.

Answer]: Analysis: When using the multimeter resistance file to measure the resistance blind pin, if the pointer is deflected to the right when the missing manuscript is large, the measured resistance value is small, and the resistance value of the anti-wear game is large.

In the measurement of the relationship between conductor current and resistance, why is the resistance value of the resistance box and the sliding variable chain nuclear resistor the maximum when the resistance value of the resistance box is the same, and the electric banquet hydraulic pressure that is controlled at both ends of the resistance box is the most small.

When the value of the resistance is maximum, because the magnitude of the resistance is inversely proportional to the current flowing, it means that the current flowing through the conductor is the smallest difference. The voltage is the value of the current multiplied by the resistance, so when the resistance of the resistance box and the sliding rheostat is maximum, the constant voltage controlled at both ends of the resistance box is the smallest.

The voltmeter is connected in parallel at both ends of the resistor, and its voltage is the voltage at both ends of the resistor.

However, the voltmeter diverts a little current, which causes the current measured by the ammeter to be larger, and the current flowing through the ammeter is set to i, and this i is directly measured and displayed by the ammeter, and the current that actually flows through the resistance is not so much.

Calculating the resistance r is calculated by dividing the voltage u read by the voltmeter by the current i read by the ammeter, i.e.:

r=u i where u is the voltage of the resistor, but i is too large, and the actual current flowing through the resistance is not so much, so the calculation is that the actual measured resistance is small.

In our current life, because of the development of science and technology, basically every household can use electricity now, but in the learning process, we will measure the resistance and current, so we will think about the accuracy of the resistance valueIn a circuit, the higher the current, the more accurate the resistance measurement? Why is this happening? For this reason, the higher the current, the more accurate the resistance measurement, and rightly so, because there is a relationship between the current and the resistance.

When we learn physics knowledge in junior high and high school, we know that there is a certain relationship between current and resistance, and the relationship between them is inversely proportional, when the current is larger, the resistance is smaller, because the measurement range of the ammeter and voltmeter is limited, so now people use to measure resistance and current, basically use Wanlian meter, and when the current is larger, the smaller the measured resistance, the smaller the resistance range value, the more accurate the measured value obtained, so the larger the current, the more accurate the measured resistance.

On the contrary, we know that after working for a period of time, the resistance of many electrical appliances will be very large, so the current at this time will be smaller, so we will feel that the current is very weak, and at this time, through the measurement of resistance and current, we can get a more accurate current value, so using the relationship between current and resistance, we can clearly know that when the current value is very large, the resistance is measured at this time, and the resistance obtained is more accurate.

But we also know that there is a certain amount of error in any experiment, even if it is man-made, we can try to avoid it, but systematic error, we can't avoid it artificially, because every machine that measures current and resistance has certain defects, if you want to improve this defect, you need human science and technology to progressBut in general, the higher the current value, the more accurate the resistance value is obtained, which is true, because there is an inverse relationship between the current and the resistance.

1.Analyze the circuit first:

Don't worry about the voltmeter first, see how the current flows (mark the current if you can), and then look at the voltmeter in the ** connection, where is the measured voltage.

2.Analyze this question.

The current flows from the positive electrode to the slip r in two ways, and flows to R1 at the merging, so the ammeter measures the voltage of the parallel connection of the slip r and the sum of the resistance of R1.

3。Why when the external resistance is greater than the internal resistance, the closer the external resistance is, the greater the output power of the power supply, set the external circuit resistance: r, power supply resistance:

r, the output power of the power supply: p, the electromotive force of the power supply is e, then: p=[er (r+r)] r=e r (r+r) =e (r+r r+2r).

This is known from the basic inequality.

When r=r, r+r r takes the minimum value.

When r=r, p=e (r+r+r+2r) has a maximum value e (4r), the outer circuit resistance is equal to the power supply resistor, and the output power of the power supply is maximum.

In the voltammetry resistance measurement experiment, because the voltmeter and ampere meter have internal resistance, it will cause systematic errors to the experimental results version. 1. When the ampere meter is connected, the voltage of the ampere meter is too large to be measured by the ampere meter R measurement = RX+Ra is large.

2. When the ampere meter is externally connected, the voltmeter shunt makes the current measured by the ampere meter larger, r measurement=rx*rv (rx+rv), that is, small.

There is also a sliding rheostat in this circuit, so the voltage distributed on the ammeter after connecting the resistor box in parallel is different from that at 1. You can assume that the voltage is 1V, the sliding rheostat is ohms, and RG is ohms. Actually do the math and you'll find out.

There is a systematic error in this, but it is an approximation that R2=Rg After the second step, because the ammeter is connected in parallel with the resistance box, their total resistance becomes smaller, and the total voltage is unchanged, so the total current of the ammeter and the resistance box becomes larger, so the current on R2 is larger than 250, and the voltage of the resistance box and the ammeter are the same, so the resistance value of R2 is less than RG

This is due to the fact that at the initial stage of entering the solution, electrolysis occurs. That is, the nano ions in the brine move to the negative electrode, while the chloride ions.

Moving towards the positive electrode, this creates a current-like ion current, direction and multimeter in the water.

The direction of the output current is the same, and the current measured by the multimeter is greater than its output current, so there will be a negative resistance at this time.

When the electrolysis is carried out for a certain period of time, the chloride ions on the positive electrode are oxidized, and the nano ions on the negative electrode are reduced, so that the electrolysis phenomenon is gradually weakened, and the current passing through the multimeter will gradually decrease, resulting in the resistance display gradually increasing, and finally becoming a positive value.