Junior high school physics voltage questions, how to explain voltage in junior high school physics

To measure the voltage of a small bulb, connect the voltage device in parallel with it. Look at this diagram and remove the voltage detector first.

As shown in the first picture.

Then install the voltage, change the position of the voltage, without changing the wiring position, you can easily see which small bulb is connected in parallel with the voltage.

Such as the second picture.

V1 is 2V, L2 = 10V, L1 = 10V1 and L2 are in series, and the supply voltage is 12V

When the switch is closed, V2 measures the voltage of L1. V1 measures the voltage of L2.

The crux of the matter: there is no pressure drop on one wire. That is, you move the two ends of the voltmeter along the wire (without crossing the device in between), and the voltage representation does not change.

The main thing is that you may not understand the diagram.

Teach you how.

First of all, remove all the voltmeters, and you will get a circuit diagram in series, the characteristics of the circuit diagram in series are that the current is equal everywhere, and the power supply voltage is equal to the sum of the voltages of each electrical appliance.

Then it's time to connect the voltmeter, which contains the power supply, but he certainly doesn't measure the power supply and the electrical voltage. Then you think of switches as wires, and appliances and power as roadblocks. Then move the wires at both ends of the voltmeter, stop when you encounter the "roadblock", of course, both ends of the wires have to be moved, if you encounter the positive error that the voltmeter contains the power supply and other electrical appliances between the two wires, look for another way to move, until the power supply and other electrical appliances are between the two wires of the voltmeter or only the power supply between the two wires.

It may be a bit tedious here, but it may be easier to understand after listening to the teacher's explanation.

Here you can tell you that V1 measures the voltage of L2, and V2 measures the voltage of L1.

So the voltage of L1 is 10V and the voltage of L2 is 2V

Power supply voltage = V1 + V2 = 2 + 10 = 12V

V1 is connected to both ends of L2, so the voltage of L2 is 2V, V2 is connected to both ends of L1, so the voltage of L1 is 10V, because L1 is connected in series with L2, so V1+V2=Total voltage=2V+10V=12V

Here's a way for you.

See if there is an L2 and a power supply sandwiched between v2.

V2 measures the supply voltage minus L2.

To put it simply, if a voltmeter is sandwiched between the electrical appliances, then the voltage measured by the voltmeter is the power supply voltage minus the voltage of the electrical appliances sandwiched in the middle.

l1=10 l2=2 supply voltage=12

V2 is connected in parallel with L1, and the voltage of L1 is measured.

V1 is connected in parallel with L2 and the voltage of L2 is measured.

L1 L2 in series So the supply voltage is the sum of the two.

No, in parallel circuits, the voltage of each branch is equal to the total voltage, if 20 bulbs are connected in parallel, then each end is 110V, if it is connected in series.

Voltage in junior high school physics is a physical quantity that measures the difference in energy between a unit charge in an electrostatic field due to different electric potentials.

The SI system of units for voltage is volts (V, abbreviated as volts), which is equal to the work done by a unit positive charge to move from point A to point B due to the action of an electric field force, and the direction of the voltage is specified as the direction from a high potential to a low potential. Voltage is the reason why the free charges move in a direction to form an electric current in a circuit.

Voltage classification

1. Divide by size.

Voltage can be divided into high voltage, low voltage and safety voltage. The difference between high and low voltage is based on the voltage value of the electrical equipment to the ground.

The voltage to the ground is higher than the resistance shirt or equal to 1000 volts of megachange is high voltage. The voltage to the ground is less than 1000 volts. Among them, the safe voltage refers to the voltage that the human body is exposed to for a long time without the risk of electric shock.

2. According to the function.

1) Impedance voltage noun. The value of the applied voltage when one winding in a two-winding transformer is short-circuited and a voltage of the rated frequency is applied to the other winding and the rated current flows through it. For a multi-winding transformer, the applied voltage value when the windings are open except for the pair of windings tested, and the rated current corresponding to the winding with the smaller rated capacity in the pair of windings flows through it.

The impedance voltage of each pair of windings is a value at the corresponding reference temperature and is expressed as a percentage of the rated voltage value of the applied voltage winding.

2) Medical voltage. The voltage in the ECG diagram refers to the distance between the two horizontal lines on the ECG diagram. It is often used to measure the amplitude of an electrocardiogram.

Units are usually expressed in mm or mV. The value of the voltage is related to the regulation of the *calibration voltage. If the input of a standard voltage of 1mV shifts the baseline up by 10 mm, the distance between the two thin horizontal lines is 1 mm, and the voltage is.

When measuring the amplitude of an ECG, voltage alignment makes sense.

Common values

1. The voltage induced by the TV signal on the antenna is about.

2. Maintain the voltage of the human biocurrent.

3. Nominal voltage of alkaline battery.

4. The voltage between the two poles of the silver oxide battery for high-voltage wire electronic watches.

5. The voltage of a lead-acid battery is 2V.

6. The voltage between the two poles of the hand-held mobile battery.

7. The voltage for human safety is generally not higher than 36V.

8. The voltage of the home circuit is 220V.

9. The voltage of the power circuit is 380V.

10. The voltage of the trolleybus power supply is 550 600V.

When S is closed, L1 is short-circuited, L2 and L3 are connected in series to sell off, V2 measures the voltage at both ends of L2, and V1 measures the voltage at the end of the road, so the voltage at both ends of L2 is 5V and the voltage at both ends of L3 is 7V;

When S is disconnected, the three bulbs are connected in series, V1 measures the voltage at both ends of L2 and L3, V2 measures the voltage at both ends of L1 and L2, the sum of the two voltmeters is the sum of the voltage of the two Tan and the voltage at the end of the road, the voltage at the end of the road is 12V in the first question, then the voltage at both ends of L2 is 1V, the voltage at both ends of L1 is 3V, and the voltage at both ends of L3 is 8V

Required test point: The voltage commonly used in the laboratory has a range, and when the 0 3V range is selected, the graduation value of the voltmeter is V; When the 0 15V range is selected, the voltmeter has a graduation value of V

Secondary Exam Questions: The following statements are incorrect:

a.A power supply is a device that provides voltage.

b.Voltage is responsible for the formation of electric current.

c.The electric current is formed by the directional movement of the charge.

d.As long as there is voltage at both ends of the circuit, there must be current.

Answer: two, answer: choose D (because as long as there is a power supply, there is voltage, and the condition for current generation is A.)There should be a power supply bThere are closed circuits. )

Solution: When the series ruler is taken, the current in the circuit i=u (6 +rx)=2v rx

When connected in parallel, the root is buried according to Ohm's law u rx=2a

Solving the equation system consisting of two formulas of liquid wax yields rx=3 u=6v

1.The voltmeter is at both ends of the power supply and the bulb, and it is clear that the voltmeter measures the supply voltage, which is the voltage applied to the bulb.

2.The total voltage of the power supply is 9V, what is the value measured by the voltmeter, it depends on how strong the load capacity of the 9V power supply is, if the load is small, the measured voltage is still 9V, if the load exceeds a certain size, the measured value will decrease with the increase of the load.

3.In a series circuit, there is a switch, a bulb, and a power supply, and when the switch closes to form a loop, the voltage at both ends of the switch is 0.

If this question is not for the language of the test, B is the correct answer. A is definitely wrong, this goes without saying. Although the C switch is disconnected, there is no disconnection between the two ends of the switch and the battery, so the voltage at both ends of the switch and the voltage source voltage are equal and not 0

b is correct, the switch is disconnected, if the voltage at both ends of the lamp is not zero, won't the lamp turn on? That would contradict the objective reality (if you turn off the switch, the light won't come on.) ）

a.The voltage at both ends of the power supply is equal to the supply voltage.

b.The voltage at both ends of the lamp is the voltage through the resistance of the bulb, which is lower than the power supply voltage cThe voltage at both ends of the switch is zero and the same as B.

d.None of the above is true. The fault lies in the above reasons.

First of all, for a. There is voltage at both ends of the power supply regardless of whether the switch is disconnected or not, when you disconnect the switch, use a suitable voltmeter to measure the voltage of the power supply, there must be a reading. For b, yes.

In fact, it is also easy to understand, have you ever seen a socket? There is a switch control kind, when you press the button will be energized, at this time the voltage tester is voltage, when the switch is turned off, there is no voltage, for c, when the switch is disconnected, the voltage at both ends of the switch is equivalent to the measured power supply voltage, not 0So d must be wrong.

There is no disconnect current, but the voltage is not zero.

First of all, a is because there must be voltage on both sides of the power supply, and b is because the bulb is close to the positive pole, so there is still voltage at both ends of the lamp and there is no current, and c is because the switch is still in a circuit, so there is still voltage at both ends of it.

A: You can measure the voltage of the power supply by connecting the voltmeter to the positive and negative poles of the power supply B: Because the switch is disconnected and the lamp is close to the positive pole, if you connect the voltmeter to both ends of the lamp, it must be voltage 0, because the circuit is open and there is no current, so there is no voltage; If you put the voltmeter over the switch, with one end between the lamp and the positive terminal, and the other end between the switch and the negative terminal, the voltage is not zero.

C: Obvious error, if it is connected to both ends of the switch, it is not an open circuit. This is similar to the second connection of b.

I wish you progress in your studies!! wish you to study well！！！

The voltage is not zero, the size is the power supply voltage, the light is not lit just the circuit is broken, and the resistance at the open circuit is regarded as infinity.

Hello, the solution to this problem is that the sum of the voltages of the small lanterns can only be greater than the voltage of the home circuit 220V, if it is less than it will quickly burn out, so at least 19 are connected in series; After the number of lamps is connected in series, the required rated voltage can be greater than 220V, which is safe, but the brightness will be appropriately reduced.

The parallel will undoubtedly burn out.

If you use parallel connection and series combination, you can also use series connection, but the whole must be connected in series, such as 20 series connections, and then use one parallel connection on any lamp, but the number of lights used in this way will be greater than that of simple series. But the two lights connected in parallel will be very dim or not bright, for example, two lights in parallel, they have to share the rated current in the series circuit, so they can't be lit, but it does not affect the brightness of the lights that are not connected in parallel.

That's detailed enough, hehe, I hope it helps you.

220 12=, so at least 19 in series can be connected.

The sum of the rated voltages of the small lanterns can be greater than the home circuit, and must be greater than or equal to.

If it is connected in parallel, the single voltage is still 220V, which will burn out.

Yes, but the brightness will be lower, and if you answer the questions, it is generally just right or just a little lower.

Series voltage divider, parallel shunt, this is very basic, and it is very simple to understand.

The small lantern must be in series circuit, and the street lamp must be connected in parallel in the circuit, the voltage voltage at both ends of each small lantern does not exceed 12V, and the household voltage is 220V, which should be 19!

The voltage should be exactly less than or equal to, if it is small, it will burn out, and if it is large, it will be dark.

It should be connected in series, because the voltage is divided in series, and shunt in parallel.