Solve, junior high school physics exam 5 today

D should be selected for this question. All four images are in series.

First, take a look at option a. At this time, the voltmeter is connected in parallel with L1L2, and the voltmeter measures the L1L2 voltage, that is, the power supply voltage. It is not the voltage of L1 as stated in the title.

option b, the positive and negative binding posts of the ammeter are reversed.

c option, the positive and negative binding posts of the ammeter are reversed.

D option, the current goes from the positive terminal of the power supply to L2 to L1 and finally back to the negative terminal. As I said at the beginning, they are all connected in series, so the current L1 measured by the ammeter. At this time, the voltmeter is connected in parallel with L1 and measures the voltage of L1. So, in line with the topic.

A voltmeter measures the total voltage, B ammeter is reversed, C ammeter is also reversed.

D voltmeter resistance is infinite, so it is regarded as an open circuit, it is equivalent to the ammeter L1L2 in series, at this time the current is equal everywhere, and the ammeter is right.

The voltmeter is connected to the L1 current inflow and the outflow is connected to the outflow, so it is also right, choose D

Select D First of all, the voltmeter is gone, is the ammeter and L1 L2 in series, and then the voltmeter is connected in parallel on L1 Secondly, pay attention to the ammeter and voltmeter from + in from - out So choose D

Choose D, BC is definitely not right, A, the voltmeter is to measure the power supply voltage.

You can judge the situation of a short circuit according to the current method, based on the principle that the current takes the conductor first.

That is to say, if the current needs to be diverted, one of the two roads has electrical appliances on it, and the other has no electrical appliances on it, that is, the wire, it will all go away from that wire, and the road with electrical appliances does not divide any current, that is, the situation that the electrical appliances are short-circuited.

If the current comes out of the power supply, and there is a wire that can be returned to the negative pole, it is a short circuit of the power supply, and the short circuit of the power supply is harmful and easy to cause disasters.

1.The magnitude of the current and the number of turns of the wire Closing and disclosing the circuit 2Electromagnetic induction coil brushes mechanical energy electrical energy 3A current that changes both frequency and direction 20 504Current Direction The direction of the magnetic field.

5.Coils, magnetic fields, electrical energy, and mechanical energy.

Current power switch.

Electromagnetic induction phenomenon.

Magnetic energy Electrical energy.

An electric current that changes direction.

First f=pvg

v=s*h is based on Figure A, because it can be seen from the image that in Figure A, the solid cylinder is completely immersed in water) can be found to be specific to S.

Second, when it is not put into the liquid at the beginning, it is 2n, which means that the gravitational force on the cylinder is 2n, then: m=p*v

And the volume of water discharged by v is equal to the volume of the cylinder, you need to state that v water = v column and then p can be found

Thirdly, it can be seen from the first figure that the beaker is 6cm high

Then p=f s

f=gg=mg

m=vpv=sh

In general, p=phg

p = density of water, h = 6cm, g is the gravitational constant

Figure B looks like soy sauce, am I wrong? Or is he really playing soy sauce. Ha ha.

(1) The gravitational force of the cylinder obtained from 2n is 2n. From Figure A, the height of the cylinder is obtained in centimeters, which is subject to buoyancy (the gravitational force of discharging water). The volume of the cylinder is 60 cubic centimeters, and the bottom area is 25 square centimeters.

2) (3) The density of the liquid is 4g cm 3 The height of the liquid is 6cm (follow the first picture, in the second picture is because the object is floating), and the pressure is calculated by yourself.

It is always the person who is hard to say what I calculated.

The second question is a typical proportional formula obtained from the floating condition, which can be calculated by using some data from the first question.

It's hard to get to the sky.

Here's what the question for junior high school students looks like.

1 v=f float pg=(cubic meter=6 cubic cms=v h=6 square centimeters

2 m=n/g=

Density = m v = cubic meters.

Solution: (1) When the lower end of the metal frame B just enters the magnetic field, the movement of the part conductor of the closed circuit in the magnetic field to cut the magnetic inductance line will produce an induced current, and the energized metal frame B is subjected to the vertical upward magnetic field force in the magnetic field, so that the force on the right end of the lever is reduced;

And plastic frame a is an insulator, will not produce induced current, will not be subjected to magnetic field force, the left end of the lever force situation remains unchanged, at this time the product of the left end of the lever force and the arm of the lever is unchanged, the product of the right end of the lever force and the arm of the force is reduced, according to the balance condition of the lever, the lever will rotate in the counterclockwise direction.

2) If the direction of the magnetic field is changed to the vertical paper side outward, the direction of the induced current generated changes, and the direction of the magnetic field and the direction of the current are changed, the direction of the magnetic field force on the metal frame B remains unchanged, and it is still vertically upward, so the rod still rotates in the counterclockwise direction.

Therefore, the answer is: when the lower end of the metal frame B just enters the magnetic field, the movement of cutting magnetic inductance lines will produce an induced current, and the energized metal frame B receives an upward magnetic field force in the magnetic field; Counterclockwise.

250n I guess you already get it.

The sliding direction of the rice belt is opposite to the direction of the conveyor belt, and the direction of friction is opposite to the relative sliding direction, that is, it is consistent with the direction of the conveyor belt.

When it then moves at a constant speed with the conveyor belt, there is neither relative motion nor relative motion annihilation tendency, so it is 0n

In this case, you can assume that there is no friction (photoclad plane), and the rice is only subject to gravity and support, so it is also stationary relative to the conveyor belt, so it is not subject to friction.

250N is 250N in the same direction as the conveyor belt

1.To make the wooden block float is to calculate the volume of water discharged when the wooden block is equal to the gravity of the wooden block, and then calculate the height of the water, multiply it by the bottom area of the container, and obtain the volume of water, and the water quality can be calculated.

2.When the temperature of aluminum and water is different, heat transfer occurs until the temperature of both is the same. So the water and aluminum are the same temperature.

First, the pressure of 20 square centimeters other than the area occupied by the wooden block is equal to the pressure of the wooden block to the ground.

Second, because the specific heat capacity of water is larger, the internal energy of aluminum is constantly transferred to water, and the temperature of so aluminum is not greater than that of water (even when boiling), just like water in a carton is burned on fire, and the specific heat capacity of paper is not greater than that of water, why not burn out.

The first is: to make the wooden block float is to say that when the buoyancy is equal to the gravity of the wooden block, calculate the volume of water discharged when the wooden block floats, and then calculate the height of the water, multiply it by the bottom area of the container, and obtain the volume of water, and the water quality can be calculated.

The first is that when the temperature of aluminum and water is different, heat transfer occurs, and the heat transfer is until the temperature is the same, so their initial and final temperatures are equal.

But in the process of heating, it may not be equal.

1 Make the block float.

That is, when the buoyancy force is equal to the gravitational force of the wooden block.

The volume of water discharged by the block can be calculated using the buoyancy formula (that is, the volume of water poured in) to calculate the mass of water.

2 During the heat transfer, the heat is transferred to the pot first and then to the water, that is, through the medium of the aluminum pot, that is, the temperature of the water is transmitted by the aluminum pot, and the heat transfer is until the temperature is the same, so their initial temperature and end temperature are equal.

But in the process of heating, it may not be equal.

1. Electromagnetic induction, internal energy.

Analysis: If the coil has resistance, it will generate electric heat, that is, electrical energy is converted into internal energy.

kg, analysis: m v 700, calorific is: q mq 7

Work: w=fs 800 1000 800000j, power: stove mountain roll p=fv 800 25 20000w=20kw

Analysis: It can be seen from the image that the speed of the car does not change when it moves in a uniform linear line, and the kinetic energy does not change, when the engine is turned off, the speed concealment decreases, and the kinetic energy decreases, but the kinetic energy is proportional to the square of the speed, so the image of kinetic energy and distance should be 2

The energy storage efficiency is 60%, and the efficiency of converting kinetic energy into internal energy is: =1-0%=40%, while EK0=375000J, W = EK0 =375000*40%=150000J

Electromagnetic induction (magneto-electric).

Internal energy (thermal energy) ("Inner World can be cautious" standard point).

7kg（m=pv=(

b (These questions are simple to calculate first, and if you calculate it correctly, choose it, and the others are ominous and use it to see it.) --If you are sure) hope.