What are the concepts of full bias and semi bias in circuits and how to apply them

The sliding rheostat should be adjusted first.

Make the ammeter fully biased, and then adjust the resistance box connected in parallel with the ammeter.

Mis-offset the ammeter.

The principle of this experiment is that since the total current in the circuit changes very little when adjusting the resistance box, that is, during the second adjustment, it can be regarded as constant, so that the other half of the current can be regarded as the process of adjusting the resistance box to make it half offset.

All flow through the resistance box, that is, the current flowing through the resistance box and flowing through.

The current of the ammeter is equal, so that there are two in parallel, and the voltage at both ends is equal, and the resistance of the two is equal.

The reasons for the low measured resistance are:

Due to the second measurement of the resistance box in parallel, the current in the total circuit should be increased, and adjusted to the ammeter half bias, the current flowing through the ammeter is half of the original is true, but the current flowing through the resistance box must be higher than half of the full deviation, the total current increases.

Therefore, the resistance displayed by the resistance box at this time should be less than the real resistance of the ammeter (both.

The voltage at both ends is equal).

Use voltammetry to measure resistance, if the circuit is connected in series, first use the resistance box and the ammeter in series, so that the ammeter is full of deviation, write down the reading of the resistance box, and then remove the resistance box, connect the unknown resistance, when the resistance makes the ammeter full, the resistance of the unknown resistance and the resistance of the resistance box are equal. Semi-bias method, which is mainly used for parallel circuits. First use the resistance box and the ammeter in series, so that the ammeter is full of deviation, write down the reading of the resistance box, in the connection of an unknown resistance, so that it is connected in parallel with the resistance box and the ammeter, when the ammeter is half, the resistance value of the unknown resistance is equal to the resistance box.

You remember two points: the series circuit has the effect of dividing the voltage, the parallel circuit has the effect of shunting, the full deviation method and the half deviation method are very important in physical experiments, there is a detailed explanation in your resource book, please gather the corresponding questions to see, it will deepen the understanding of the full deviation method and the half deviation method!!

1. The principle and application of the semi-bias method.

The internal resistance of the power supply is small and can be ignored. Close the K1 to adjust the sliding rheostat first.

Make the G meter full deviation, close K2 again, and adjust the resistance box.

Make the g table half-off, at which point rg=r. (The resistance of the external circuit is very large, and the current can be considered constant).

2. The principle and application of the full bias method.

Principle: The internal resistance of the power supply is very small and can be ignored. Close K1 first, adjust the size of R1 to make the ammeter.

Full bias, then close k2 to reduce r1 to half of the original, adjust r2 so that the ammeter is still full bias. then rg=r1r2 (2r+r1).

Knowledge Expansion: The Principle of Voltammetry Resistance Measurement:

Take advantage of Ohm's law for partial circuits.

i=u r gives r=u i. If the voltage deficit at both ends of the resistor to be measured and the current in the resistor can be measured, the solution can be measured accordingly. If there is no explicit measurement of voltage or current in the circuit, the indirect solution method of voltage or current should be analyzed in the circuit. Systematic error.

Tables A and V are considered ideal.

1. Measurement circuit form:

1) Basic form:

Inscribed method: External inscribed method:

2) Common deformations:

1) Two ammeters: Qinghui accompanying.

Principle: Knowing the internal resistance of A2, the range and the maximum withstand voltage of A2 and A1 are close, the A2 meter is regarded as a voltmeter.

2) Twin Volt Meter:

Principle: The principle that the internal resistance of v1 is known and the series current is equal is used to solve the problem.

3) Dual ammeter measurement of internal resistance:

Principle: The current in the resistance box is the difference between A2 and A1, and the resistance can be direct.

read, so the internal resistance of A1 can be measured.

4) Ammeter and resistance box:

Principle: Change the resistance of the access circuit by switching to ensure that the current is the same, then r=rx

5) Volt meter and resistance box:

Principle: Change the resistance of the access circuit by switching to ensure that the voltage is the same, then r=rx

6) The internal resistance of the ammeter:

Semi-bias method: principle: the internal reputation of the power supply is very small and can be ignored. First close K1 to adjust the sliding rheostat to make the G meter fully biased, then close K2, adjust the resistance box to make the G meter half offset, at this time RG=R. (The resistance of the external circuit is very large, and the current can be considered constant).

Full bias method: principle: the internal resistance of the power supply is very small and can be ignored. After closing K1 and adjusting the size of R1 to make the ammeter fully biased, then closing K2 to reduce R1 to half of the original, adjusting R2 to make the ammeter still fully biased. then rg=r1r2 (2r+r1).

The two principles are the same, if the half-bias method is used to measure the voltmeter.

Resistor, the schematic is a large colonized resistor connected in series on a sliding rheostat.

Then place the voltmeter and a resistance box.

After series connection, and then at both ends of the rheostat. First of all, the resistance box is short-circuited, adjusted to make the voltmeter full deviation, after the hidden banquet, only search for the active resistance box, adjust the resistance box (at this time no longer short circuit), so that the voltmeter is half off, then the resistance of the resistance box is the resistance value of the voltmeter, it can be understood in this way: set the full bias voltage of the voltmeter to U, after the adjustment, the voltage at both ends of the voltmeter and the sliding rheostat is U.

After adjusting the resistance box, because the large resistance increases when it is connected in parallel, it can be considered that the current in the circuit does not change, so the voltage at both ends of the sliding rheostat is still U, and the voltmeter is assigned to U 2, so the resistance box is also assigned to U 2. So the resistance of both is equal.

Half-bias measurement ammeter.

In the case of internal resistance, the measured value is less than the true value. When S1 is closed, adjust R to make the current express to full deviation, and the current value is set to I, I=E (R1+RG), when S2 is closed, adjust R1 in parallel with the ammeter to make the ammeter half biased, then we remember R1 as the internal resistance of the ammeter. But in the actual situation, when S2 is closed, the combined resistance of RG and R1 is RGR1 (R1+RG), which is smaller than RG and leaks silver, so the current of the total circuit will be greater than the I value, and the current flowing through R1 will be greater than I 2 because the current flowing through the ammeter is I 2, so the current value flowing through R1 will be greater than I 2.

From the shunt theorem, it can be seen that if R1 is less than much greater than Rg, the smaller the amplitude of the current increase brought by parallel R1, so the error will be smaller. The larger the e, the more the ammeter is full of offset.

and internal resistance are fixed values, then the value of r should be increased.

When the half-bias method measures the internal resistance of the voltmeter, the measured value is greater than the true value. A similar reasoning can be made here from the above explanation of the measured internal resistance of the ammeter. I won't explain it here.

These two principles are the same, if the half-bias method is used to measure the resistance of the voltmeter, the schematic diagram is a large colonization resistor in series on a sliding rheostat, and then the voltmeter and a resistance box are connected in series at both ends of the varistor. First, the resistance box is short-circuited, adjusted so that the voltmeter is fully biased, and then only the resistance box can be moved, and the resistance box is adjusted (no longer short-circuited), so that the voltmeter is half off, and the resistance value of the resistance box is the resistance value of the voltmeter, which can be understood in this way: set the full bias voltage of the voltmeter to U, and after the adjustment is completed, the voltage at both ends of the voltmeter and the sliding rheostat is U.

After adjusting the resistance box, because the large resistance increases when it is connected in parallel, it can be considered that the current in the circuit does not change, so the voltage at both ends of the sliding rheostat is still U, and the voltmeter is assigned to U 2, so the resistance box is also assigned to U 2. So the resistance of both is equal.

Try to analyze the half-bias method of measuring the internal resistance of the ammeter yourself. If you don't know much about this test error analysis, that is, the solution measures, please feel free to ask.