Ask junior high school physics electricity questions, professionals

This depends on what stage you learn in, you are in junior high school, there should be no indication of the voltmeter, because the resistance of the ammeter is too small, and the voltage of the voltmeter and the bulb on the pointing road is equal to the voltage at both ends of the ammeter, according to the resistance calculation formula of the parallel circuit, their resistance is very small, the voltage is very low, so the number of the voltmeter can be ignored.

No, the internal resistance of the voltmeter is very large, which is equivalent to a large resistance, and the internal resistance of the ammeter is very small, which is equivalent to a wire, and it can be used as a voltmeter to be short-circuited by the branch where the ammeter is located! So there is no indication!

There are no real numbers in voltmeters.

Analysis: In a parallel circuit, current flows out of the positive terminal of the battery through the dry current.

It is then divided into two branches, and the current travels from the two branches and finally returns to the negative electrode of the battery.

The first branch: voltmeter and light bulb.

The light bulb is also ohms, and the voltmeter is several thousand ohms, so the proportion of the light bulb in the secondary branch current is very small and negligible.

That is, the first branch can be regarded as a voltmeter.

The second branch: ammeter.

Because the ammeter can be regarded as a wire, the circuit is short-circuited, and the voltmeter has no number.

If you add another switch, so that one branch has an ammeter, a bulb, a switch, one is a voltmeter and a bulb, and the dry circuit is a power supply, then the current indicates that the number of changes is constant?

No change. The first question you asked was short-circuited, and the ammeter burned out.

You haven't changed the ammeter yet, how can there be an indication?

Of course, if you change an ammeter, that's a different story.

The resistance of the ammeter is too small, rarely more than 1 ohm, connected in parallel, the whole parallel part is smaller, the voltage representation can be said to have, but it is particularly small, almost ignored, if it is a junior high school, high school, it is best to choose no indicator, and the university has it.

The internal resistance of the ammeter is very small and equivalent to the wire, and the internal resistance of the voltmeter is very large and equivalent to a large resistance, which is equivalent to the voltage at both ends of the wire.

Was short-circuited, so there was no 、、、

<> from the diagram above, the answer is A

I am a family member of Ma Junqi, Ma Junqi is a second-degree disability, and he was hospitalized first, and he could have been reimbursed if he didn't get his disability in a hurry

Put the power supply and switch on the bottom line, put the small bulb on the top line, and the rest will not change, and you'll be fine.

The parallel connection method of the resistor is right, the adjustment range has become smaller, the problem is that the bulb and the power supply had better add a safety resistor, otherwise it is easy to be burned, if the value range is not given, I can't say whether your answer is correct.

The underside of the bulb is just a divider circuit.

When you move the sliding rheostat to the far left, the resistance is maximum, the current is minimum, and the bulb is off; Move the sliding rheostat to the far right, the resistance is 0, and the current is maximum.

Try connecting the bulb in series with the rheostat, and that's what my desk lamp is. Try!!!

Set the salt has xg

First of all, the density and volume of the brine can be calculated to have a mass of 420g

Then the water is (420-x)g, and the volume is (420-x)cm3x + (420-x)=400

The solution is x=

Let the brine weigh m, then the volume of salt = m

Weight of salt = m-400*1

m-400)/(m/

m = then the salt of the line =

I shouldn't be able to do it.

Doesn't it mean that volumes can't be added or subtracted?

Ball C first touches A to take away half of the charge, and ball B contacts first neutralizes and drops half of the charge and then takes away half of the remaining charge, and ball B has twice the charge left. The Coulomb force formula is directly proportional to the product of the electric charge of two point charges, so yes.

Suppose that the original charges are all q, and the polarity is opposite because it is attractable.

The contact between C and A is divided into Q 2

C is in contact with B, first canceling Q 2, and then bisecting, and the result is that B leaves Q 4 force to become F (2*4) = F 8

The amount of change in kinetic energy is equal to the sum of the work done by the forces experienced by the object. The amount of mechanical energy change is equal to the sum of the work done by other forces except gravity and elastic force.

Gravity and tension do positive work, so wf=a, wg=c;

The supporting force of the inclined plane does not do work on the object, and the frictional force does negative work, so w oblique = -b;

Air resistance does negative work, so w gas = -d

Therefore, fill in the first blank [a-b+c-d], and the second blank removes the work done by gravity, and fills in [a-b-d].

In reverse, it is a uniform acceleration linear motion with zero initial velocity.

s=1 2at 2 substitute t=1s.

Get a = 2m s 2

Substituting t=1s gives a displacement of 9m in 3s

The average velocity of the object during these 3s is .

v average = 9m 3s = 3m s

Answer: B

The distance that the object travels in the last period of time is proportional to the square of that time (because it corresponds to an inverted uniform acceleration motion).

Then it's 9 (1*3 2).

b This kind of problem is most convenient to think about the other way around--- and accelerate from 0:

s1=1/2at^2=1

a=2m/s^2

s3=1/2*2*3^2=9m

The average velocity v=s3 3=9 3=3m s

It should be a uniform deceleration, choose b, walk 1m in the last second, walk 3m in the penultimate second, walk 5m in the third second, this should be known, and then (1+3+5) 3=3 choose b

Please specify.