The current problem of series parallel circuits, the relationship between current and voltage in ser

The physics teacher said that the trunk current in the parallel circuit is equal to the sum of the currents of each branch, and the trunk circuit changes with the branch, for example, a parallel circuit with 2 bulbs, and the current is 1A each, then the trunk circuit is 2A; If you merge another bulb, the trunk circuit becomes 3A, and the brightness of the original 2 bulbs does not change, right?

A: This is true in the case where the power supply is an ideal constant voltage source. The so-called ideal constant voltage source means that the output voltage of the power supply is constant no matter what the situation.

If so, your statement above is correct. However, power supplies often have internal resistance, and if the influence of the internal resistance of the power supply is considered, the situation is different.

Suppose the internal resistance of the power supply is r, the resistance of the bulb is r, and the electromotive force of the power supply is v

When the circuit is connected to a bulb, the current i=V (R+R)=1A

When a bulb is connected in parallel, the current i=v (r 2+r), which obviously cannot be equal to 2a.

Therefore, the physics teacher's statement assumes that the internal resistance of the power supply is equal to 0. This statement is incorrect when the internal resistance of the power supply is not equal to O.

1.Is this true regardless of whether the power source is a battery or a wire?

My explanation above is correct for all circuits.

2.The current can be changed, is there anyone who can explain the reason, I don't understand why the total current can change.

According to Ohm's law: U=IR, in this formula, since U is invariant, when R changes, I must change.

3.What about series circuits? After one more appliance is added in series, the total current remains the same? Increase? (It seems that the light bulb is dimming).

It's the same in a series circuit, U=IR, in this formula, because U is constant, when R changes, I must change, and a resistance in series makes R bigger, so I has to be smaller, so the bulb is dark.

4.If the total current in the previous question does not change, please explain why the parallel change and the series connection do not change; If the total current increases, why do I remember the bulb is dim?

The current becomes smaller, so the bulb is dimmed.

5.The total current in a circuit will change, so will the total voltage change if the power supply remains the same?

The output current of the constant current source is always constant, and the output voltage of the constant voltage source is always constant. When the power supply is a constant current source, when the load resistance of the external circuit changes, the current does not change, and the voltage will definitely change, as for the basis, it is the ohm's law above.

1。Be. 2。After parallel connection, the total resistance changes but the voltage does not change, so the current is variable.

3。The total current decreases and becomes darker.

4。Because the series is divided by voltage and the current is divided in parallel, Ohm's law is followed.

5。The change in current in a general circuit is due to resistance rather than voltage.

In short, it is important to remember that there is voltage before there is current.

1: Yes The voltage on both sides of the parallel bulb is the power supply voltage (if there is no series bulb in series) 2: Of course, the total current can be changed The resistance changes the current to change i u r total.

3: The total current must change, the resistance is large, the current is reduced, and the bulb will be darkened.

5: How can the total voltage change The total voltage is fixed The current is calculated based on the voltage and resistance.

Understood, didn't understand, asked.

As the number of parallel appliances increases, the internal resistance of the power supply will of course increase, and the power supply of the power supply will of course become smaller!

If you think about it, the reason why the light bulbs in your home dim during peak power consumption is because the power supply to the lighting circuit does not reach 220 volts.

The relationship between series and parallel current and voltage is as follows:

In a series circuit, the current is equal everywhere and equal to the loop current, and the higher the resistance, the higher the voltage and the greater the power consumed; The sum of the voltages divided by each resistor is equal to the total voltage. In parallel circuits, the voltages are equal everywhere and equal to the supply voltage, the smaller the resistance, the greater the current, and the greater the power consumed; The sum of the currents of each parallel circuit is equal to the total current of the power supply.

Series circuit: current relationship: the current in the series circuit is equal everywhere, voltage relationship: the total voltage at both ends of the series circuit is equal to the sum of the voltages at both ends of each series part;

Parallel circuit: current relationship: the current in the trunk circuit is equal to the sum of the currents of each branch; Electrical relationship: The voltage of each parallel branch of the parallel circuit is equal

Therefore, the answer is: the currents are equal everywhere, and the total voltage at both ends of the series circuit is equal to the sum of the voltages at both ends of each series part; The current in the trunk circuit is equal to the sum of the currents of each branch; The voltages at both ends of each parallel branch are equal.

In a series circuit, the current is equal everywhere and equal to the loop current, and the larger the resistor, the higher the voltage and the greater the power consumed; The sum of the voltages divided by each resistor is equal to the total voltage.

In parallel circuits, the voltages are equal everywhere and equal to the supply voltage, the smaller the resistance, the greater the current, and the greater the power consumed; The sum of the currents of each parallel circuit is equal to the total current of the power supply.

Since there are several branches in parallel, the current is divided into branch sub-current and total current of the main part, and their relationship is that the total current = the sum of the sub-currents, that is, i = i1 + i2 + i3 + ......There is only one way in series, so the currents are equal everywhere, i.e. i=i1=i2=i3=......

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.

When linear time-invariant resistor elements are connected in parallel, the parallel combination is equivalent to a resistive element, and its conductance (the reciprocal of the resistance) is equal to the sum of the conductance of each parallel resistor, which is called the equivalent conductance of the parallel combination, and the reciprocal of its leakage is called the equivalent resistance. The components in Figure 1 are resistors, the resistors are R1, R2, and R3, and their conductances are G1, G2, and G3 respectively.

The law of current in the rolling circuit of series and parallel electric song: parallel circuit: parallel circuit is one of the two basic ways to make the current between the circuit elements that constitute parallel connection have more than one independent path of each other.

Serial and parallel circuits, circuit physical drawing formula: the first head is connected, the tail is connected, the first in and the tail are out. The law of current in series-parallel circuits:

Parallel circuit: The parallel fiber circuit is one of the two basic ways to make the current between the circuit elements in parallel have more than one independent path of each other, which is one of the two basic ways to form the circuit. Series and parallel circuits, circuit physical drawing method formula:

The first head is connected, the tail is connected, the first in and the tail out.

The law of current in a series-parallel circuit is as follows:

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.

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.

Ammeter Connection Rules:

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

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

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

4. You can't directly block Jianyou from connecting to the two levels of power supply.

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 series and parallel circuits, the law of current is as follows:

1. The current law in the series circuit: The series circuit refers to the circuit where the current has only one path to flow. In a series circuit, the current remains constant as it passes through each element in the circuit.

According to Kirchhoff's current law, the distribution of current in each element of liquid is the same in a series circuit. All components connected in series will be subjected to the same current. When the current enters the series circuit from the power supply, it passes through each component in series in turn, and the total current remains the same.

2. The current law in the parallel circuit: The parallel circuit refers to the circuit where the current has multiple paths to choose from. In a parallel circuit, the total current is equal to the sum of the currents in the individual parallel branches.

According to Kirchhoff's current law, the current entering a parallel node is equal to the sum of the currents leaving the node. In parallel circuits, the current is shunted according to the resistance of each branch. A branch with a lower resistance will experience more current, and a branch with a higher resistance will experience a comparatively smaller current.

The way in which the current is formed

1. DC current: DC current refers to the current flowing by charge carriers in the same direction and at a constant speed in a circuit. The formation of a DC current is usually driven by a constant voltage provided by a stable voltage source.

2. AC current: AC current refers to the current flowing in the circuit in an alternating way by the charge carriers of the missing object. The formation of this current is generated by the AC power source, and the voltage alternates positive and negative changes with time.

3. Ion current: Ion current refers to the current at which charged particles are ions. Ions are usually produced by the ionization process, and they move at different speeds and directions under the action of the electric field force.

4. Thermal electron flow Thermal current: Thermal electron flow is the flow of electrons caused by a temperature gradient. When one end of the material is hotter than the other, the free electrons flow in the direction of the lower heat due to thermal motion.

5. Electric current in semiconductors: In semiconductors, electric current is formed by the movement of electrons and holes. In the process of conducting electricity, the main factors that control the current of semiconductor devices are the diffusion and drift of electrons and holes.