How do you determine the direction of current in a parallel circuit?

Since the meter is different in junior high and high school, let's talk about the judgment of junior high school first.

When I was in junior high school, I used the voltmeter as an open circuit and the ammeter as a wire.

Closing the switch, since the switch is connected at this time, it is regarded as a wire, R2 is short-circuited, and no current passes through. Thus the current flows through the positive pole R1 (no current flows through the voltmeter), the switch, the ammeter, and finally the negative pole.

In high school, the voltmeter is considered a large resistance, and the ammeter is a small resistance.

R2 is still short-circuited, so the current can only flow from B to A.

You're a junior high school student, right?

In junior high school, when analyzing a circuit, the voltmeter can be seen as an open circuit that can be removed, so at point m, the current will only go below R1 to the right.

The current that goes below R2 will be hindered by R2, but the switching current that goes above is not hindered, so the current does not go to R2, and R2 is short-circuited.

Here are a few things to keep in mind:

1.Two points in a circuit where the wires are directly connected can be seen as the same point;

2.The branch where the voltmeter is located is equivalent to an open circuit, 3An ammeter is equivalent to a short circuit.

It depends on what kind of circuit it is, whether it is a single power supply or a multi-power supply, if you have a single power supply, you draw an arrow from the positive electrode line, and when you encounter a fork, you will be shunted, and when you encounter a parallel port, you will have to analyze it.

。。All right.. I'm going to bubble ... It doesn't matter if he's in junior high school or high school, it's not over with a meter...

The law of current in parallel circuits.

It reads as follows:

1. Series circuit.

1. The voltage law of the series circuit: the total voltage at both ends of the series circuit is equal to the sum of the voltages at the two ends of each electrical appliance.

That is: u=u1+u2.

u1∶u2∶u3=ir1∶ir2∶ir3=r1∶r2∶r3。

p1∶p2∶p3=i2r1∶i2r2∶i2r3=r1∶r2∶r3。

2. Characteristics of series circuit:

1) There is only one path for the current.

2) The switch controls the on/off of the entire circuit.

3) Mutual influence between electrical appliances.

3. The current law of series circuit: i=i1=i2.

2. Parallel circuit.

1. The law of parallel circuit.

1) The voltage of each branch in the parallel circuit is equal and equal to the power supply voltage. u=u1=u2。

2) The dry current (or total current) in the parallel circuit is equal to the sum of the currents of each branch. i=i1+i2。

3) The reciprocal of the total resistance in the parallel circuit is equal to the reciprocal sum of the resistance of each branch. 1 r=1 r1+1 r2 or written as: r=r1*r2 (r1+r2).

4) The ratio of the current of each branch in the parallel circuit is equal to the inverse ratio of the resistance of each branch. i1/i2=r2/r1。

5) The ratio of the power of each branch in the parallel circuit is equal to the inverse ratio of the resistance of each branch. p1/p2=r2/r1。

6) Parallel circuit: Adding electrical appliances is equivalent to increasing the cross-sectional area of resistance Definition: electrical appliances are connected in parallel in the circuit.

Features: The circuit can be divided into trunk circuit and branch circuit, one branch is disconnected, and the other branch can also form a current path, so the circuit fault can not be eliminated by short-circuit method.

Uses: household circuits, modeling lamps for large buildings, urban street lights; Shunt.

2. Characteristics of parallel circuit:

1) The circuit has several paths.

2) The trunk switch controls all the electrical appliances, and the branch switch controls the electrical appliances of the branch where it is located.

3) The electrical appliances have no influence on each other.

1. The characteristics of the parallel circuit are that the voltage in the two lines is equal, and the current changes with the change of the resistance value, the resistance increases, the current decreases, the resistance decreases, and the current increases.

2. The relationship between the current in the parallel circuit: when the two resistance values in the parallel circuit are equal, the current intensity is the same, when their resistance values are not the same, the current in the line with low resistance value increases, and the current in the line with high resistance value decreases.

3. The relationship between voltage and current in parallel circuits

1. The voltage of each branch in the parallel circuit is equal and equal to the power supply voltage: u=u1=u2.

2. The dry circuit current (or total current) in the parallel circuit is equal to the sum of the branch currents: i=i1+i2.

3. The reciprocal of the total resistance in the parallel circuit is equal to the reciprocal sum of the resistance of each branch, 1 r=1 r1+1 r2 or written as: r=r1*r2 (r1+r2).

4. The ratio of the current of each branch in the parallel circuit is equal to the inverse ratio of the resistance of each branch: i1 i2=r2 r1.

5. The ratio of the power of each branch in the parallel circuit is equal to the inverse ratio of the resistance of each branch: p1 p2=r2 r1.

Parallel circuit diagram.

Answer; The parallel circuit voltage is equal, so u=i total * r total.

i-branch = u r-branch i1 i2=r2 r1 This is because of the series partial pressure.

The specific process is as follows.

Parallel connection. ∴ u=u1=u2

i=u/ri1/i2=(u1/r1)/(u2/r2)=r1/r2

Parallel connection. 1. Parallel connection is a connection mode between components, which is characterized by connecting two components and devices of the same or different classes, and at the same time, the tail and tail are also connected. It is usually used to refer to the way in which the electronic components in a circuit are connected, that is, parallel circuits.

2. Parallel connection is to connect the two terminals of each element of two or more two-terminal circuit elements to a pair of common nodes respectively.

Connections of various electrical appliances in the home. In the parallel circuit, the switch on the trunk road is closed, the switch on the branch road is closed, the bulb will shine, the switch on the trunk road is disconnected, the switch on each branch road is closed, and the bulb will not emit light, indicating that the switch on the trunk road can control the entire circuit, and the switch on the branch road can only control the branch.

4，.Characteristics of series circuit and parallel circuit: In series circuit, since there is only one path of current, the current flowing from the positive terminal of the power supply will flow through each consumer one by one, and finally return to the negative terminal of the power supply.

Therefore, in the series circuit, if one of the electrical appliances is damaged or disconnected somewhere, the whole circuit will become an open circuit, the circuit will have no current, and all the electrical appliances will stop working, so in the series circuit, several electrical appliances are implicated in each other, either all of them or all of them stop working. In a parallel circuit, the current flowing from the positive terminal of the power supply is divided into two branches at the branches, each with current flowing through it, so that even if one branch is disconnected, the other branch will still form a path with the trunk circuit. It can be seen that in a parallel circuit, the branches are not implicated with each other.

5. Two or more switches are connected in parallel to form a logic "or circuit". Assuming that the power supply is connected to both ends of the circuit, current will flow as long as either switch is closed.

The law of current in series-parallel circuits: the currents in various parts of the series circuit are equal, and the currents on the trunk circuit in the parallel circuits are equal to the sum of the currents in each branch.

1 current. Current is a physical quantity that indicates the strength of the current, usually represented by the letter i, and its unit is ampere, referred to as amperes, and the symbol is a. Some devices have very small currents, so usually we also have the following smaller units: milliamps and microamps.

2. Ammeter connection rules.

1.The ammeter must be connected in series with the electrical appliance being tested;

2.The measured current should not exceed the range of the ammeter;

3.The connection of the binding post should be correct;

4.It cannot be connected directly to the power supply stage.

3. The difference between series and parallel.

Series circuit: A circuit composed of connecting components one by one. Features are:

The current flowing through one element also flows through the other. For example: small lanterns at festivals.

In the series circuit, the switch is closed, the two bulbs emit light at the same time, and the two bulbs are off when the switch is disconnected, indicating that the switch in the series circuit can control all the electrical appliances.

Parallel circuit: a circuit composed of connecting components in parallel, characterized by the fact that the current of the trunk circuit is divided into two parts in the branches, and flows through each element in the two branches respectively.

For example: the connection of various electrical appliances in the home. In the parallel circuit, the switch on the trunk road is closed, the switch on the branch road is closed, the bulb will shine, the switch on the trunk road is disconnected, the switch on each branch road is closed, and the bulb will not emit light, indicating that the switch on the trunk road can control the entire circuit, and the switch on the branch road can only control the branch.

In a series circuit, the currents are equal everywhere, and the total voltage is equal to the sum of the voltages of each branch;

In a parallel circuit, the voltages are equal everywhere, and the total current is equal to the sum of the currents of each branch.

In a series circuit: the current of each resistor is the same, and the total resistance is equal to the sum of the resistors

The law of current in parallel circuits.

The voltage of each resistor in a voltage parallel circuit is the same as the total voltage.

The general principle is:

Wiring method: The ammeter is connected in series with the part of the circuit to be measured.

Select Range: It is not possible to measure currents that exceed the range of the ammeter. If it is not possible to estimate, try the touch with a larger range, and if the pointer does not exceed the small range, use a small range measurement instead.

It is important to note that when connecting the circuit, the current flows in from the "positive" terminal of the ammeter and out from the "negative binding post".

The specific method: The following figure is to measure the current in the bulb L1.

The diagram below is a measurement of the current in L2.

The figure below is a measurement of the total trunk current.

Hello, I'm here to help you, I hope I can help you, thank you.

Series circuits. Parallel circuits.

Current. Peculiarity.

The current is equal everywhere in a series circuit.

i＝i1=i2=……

1. The current in the trunk circuit in the parallel circuit is equal to the sum of the currents of each branch.

i＝i1i2

2. The current in each branch is inversely proportional to the resistance of each branch.

i1:i1=r2:r1

Voltage. Peculiarity.

1. The total voltage at both ends of the series circuit is equal to the sum of the voltages at both ends of each part of the circuit.

u＝u1u2

2. The voltage at both ends of each section of the circuit is proportional to the resistance of each section of the circuit.

u1:u2=r1:r2

The voltages at both ends of each branch of the parallel circuit are equal.

u＝u1=u2=……

Electrical power characteristics.

1. The total power of the series circuit is equal to the sum of the power of each section of the circuit.

2. The electrical power of each section of the circuit is proportional to the resistance of each section of the circuit.

p1:p2=r1:r2

1. The total power of the parallel circuit is equal to the sum of the power of each branch.

2. The electrical power of each branch is inversely proportional to the resistance of each branch.

p1:p2=r2:r1

Parallel: The voltage at both ends of each branch is equal and equal to the total voltage (supply voltage).

The sum of the currents of each branch is equal to the total current (trunk current).

Application of Ohm's law for series and parallel connections:Current.

Tandem: i1 = 12 = total. Parallel: i1 + 12 = i total. Voltage.

Tandem: u1+1u2=1u3. Parallel: u1=u2=utotal. Resistance:

Series connection: R1 R2 R1+R2 (two resistors only).

Parallel: 1 ri+2 r2+3 r3+1 rn (multiple resistors.

Series partial pressure: u1 u2=r1 r2. Parallel shunt: i1 i2=r1 r2.

Circuit Variation Maximums Problem:1. The variation range of the dynamic circuit meter.

It is only necessary to take the left and right limit conditions and calculate them separately.

2. The variation range of the dynamic circuit sliding rheostat.

Determine how voltage and current change with sliding rheostat resistance.

Find out the maximum voltage and current, and who dies first.

Find the maximum and minimum value of the sliding rheostat.

1.The terminal voltage of all parallel components is the same voltage.

2.The total current of a parallel circuit is the sum of the currents of all the components.

Example: Residential lighting bulbs are connected in parallel to a power supply with a rated voltage of 220V, so each bulb is subjected to a voltage of 220V, and the total current of the external circuit is the sum of the currents flowing through all the bulbs.

Series and parallel connection are the two most basic forms of circuit connection, and there are certain differences between them. To determine whether the components in a circuit are connected in series or parallel, it is necessary to grasp their basic characteristics.

Here's how:

1) Electrical connection method: analyze the connection method of electrical appliances in the circuit, and connect them in series one by one; Parallel between two points in a circuit is parallel.

2) Current flow direction method: when the current flows out of the positive terminal of the power supply, it flows through each component in series in turn; When two branches flow through a certain point key mountain, and finally close to a bright pants, it indicates that the circuit is in parallel.

3) Removal of component method: arbitrarily remove an electrical appliance to see whether other electrical appliances are working normally, such as all electrical appliances have been removed, and other electrical appliances can continue to work, then the connection relationship of these electrical appliances is parallel; Otherwise, it is tandem.

4) Use a pen line instead of a wire, and use a wire to connect all electrical appliances in series, and if not, it is in parallel.