Finding Ohm s law and its application is a little more difficult and researchy!!

The slide p moves to the left, the wire length becomes shorter, the resistance becomes smaller, the current becomes larger, and Table 2 increases whether it is an ammeter voltmeter. Therefore, BC. is excludedIf 1 3 is an ammeter and R2 is short-circuited, only A remains.

It should also be noted that when this kind of meter is normally connected in parallel with the electrical appliance, it must be a voltmeter, and the channeling connection is an ammeter, so that it can be seen directly without the elimination method. I'm on the third year of junior high school.,Just finished the sliding rheostat in the morning.,About Ohm's law before the barely cleared.。。。

Choosing a voltmeter is when that meter and line don't exist. An ammeter is when that meter is a line.

p shifts to the left, the resistance becomes smaller, the voltage does not change, so the current becomes larger. i=u/r

qyj123qyj, the analysis is correct! Exclusion method: either in series or in parallel, if a is feasible in series, if it is connected in parallel, 2 tests that the voltage at both ends of the power supply remains unchanged, c and d are not right, and finally choose a

Two conductors with different resistances are connected in parallel: the higher the resistance, the smaller the passing current, and the larger the passing current of the conductor with less resistance.

Supply voltage. Total resistance.

Known: i-an.

i1 amps. r2 = 6 ohms.

Seek: r1; u；r

Solution: R1 and R2 are connected in parallel.

i2 i-i1=An'an=An'an.

According to Ohm's law, u2 = i2r2 = ampere 6 ohm = volts.

R1 and R2 are connected in parallel.

u=u1=u2=volts.

R1 U1 I1 Volt-ampere 12 ohms.

r u i volt-ampere 4 ohms.

Or make use of formulas.

Calculate the total resistance).

A: (omitted).

1.In Ohm's law, it is necessary to change the voltage at both ends of the conductor, you can use the method of (changing the supply voltage), or better (connect a sliding rheostat in series in the circuit to divide the voltage); At the same time, it is also necessary to keep the voltage at both ends of the circuit constant, you can choose a power supply with a very stable voltage, and the better way is to connect a sliding rheostat in series in the circuit to adjust the voltage), and at both ends of the resistance (in parallel with a voltmeter to observe whether the voltage remains unchanged after adjustment).

2.The relationship between current and voltage and resistance is studied. In order to improve the accuracy of the experiment, the ammeter should use the ( ) range as much as possible, and the voltmeter should use the (3V) range as much as possible.

When the switches S1 and S3 are closed and S2 is disconnected, the number of currents is expressed as.

At this time, R1R2 is connected in parallel, R=R1R2 (R1+R2), U=IR = .1)

When closing S1 and disconnecting S2 and S3, the current is expressed as .

At this point only R2 is energized, U=IR2 = ..2)

When S2 is closed and S1 and S3 are disconnected, the power consumption of R2 is 2W

In this case, r1r2 is connected in series, r=r1+r2, i=u (r1+r2), p2=i 2r2 =u 2r2 (r1+r2) 2=2 .3)

Substitute (2): u= into (1) and (3) to obtain:

From (4): 3r1=r1+r2,r1=2r2 ..6)

Substitute (6) into (5) to get: (, solution:

r2=72ω

Substituting R2=72 into the potato segment (2) obtains:

Supply voltage y==36V

Substituting r2=72 into (6) yields: r1=2r2=2*72=144

When S1 is closed, S3 disconnects S2, R1R2 is connected in parallel.

Current through r1 i1 = u r1 = 36 144 =

If R2 is replaced with a sliding rheostat of "50, R2 allows the maximum current, R2 U I2=36

The total current is i=i1+i2=, and the range of the ammeter is "0 3A", and the maximum current of the circuit is 3A

The minimum value of resistance in the circuit connected to the sliding rheostat is.

The circuit is a series circuit of R1 and a sliding rheostat.

V1 measures the R1 voltage.

The ammeter measures the current of the circuit.

V2 measures the voltage across the sliding rheostat.

Because it slides from A to B.

Therefore, the resistance of the sliding rheostat decreases.

The total resistance of the circuit decreases, the circuit current increases, the current representation increases, the R1 sharing voltage increases, and the V1 indicator increases.

The power supply voltage remains unchanged, the R1 voltage increases, so the sliding rheostat voltage decreases, and the ratio of the V2 indicator decreases the voltmeter V1 and the ammeter A is the R1 resistance value, which is unchanged.

v1 measures the supply voltage.

The ammeter measures the current through a sliding rheostat and a fixed-value resistor.

V2 measures the voltage across the sliding rheostat.

Because it slides from A to B.

So the resistance decreases.

Therefore, the voltage at both ends of the sliding rheostat decreases.

Therefore, the voltmeter V2 indicates that it decreases.

So choose C