Find 40 physics experiment questions in the first half of the second year of junior high school

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Problem description:1Method: Put a raw egg in a cup of water, then gradually add salt to the water and dissolve it, pay attention to what happens, and ask questions about this phenomenon.

2.Method: Carefully pour water and cooking oil (one small glass each) along the walls of the cup into a deep glass, and then add a grape or a small candle to observe the phenomenon and ask questions.

I did, but I didn't find anything, I'm new to the subject of physics, please help, thank you.

Analysis: Experiment 1: Eggs will sink to the bottom of the cup when placed in clean water, because the density of eggs is greater than that of water, put salt in the water until saturated If there is no phenomenon, the density of concentrated brine is still not as large as that of eggs.

Experiment 2: Slowly pour water and cooking oil into the cup, you can find that the water is under the oil, because the density of water is greater than that of oil, and then put in a candle or grapes, it will also sink, but the speed of sinking in the oil layer and the water layer is different!!

You can set the standard steps in the textbook.

The idea is: measure the side length a of the cube, hook the metal block with the dynamometer and put it into the sink, and record the data according to the depth b1 and (gravity minus the dynamometer reading at the moment) according to the depth b1 and (gravity minus the dynamometer reading at the moment). It is important to note here that the metal block should not be completely submerged in the water.

The formula used for nuclear nuclear arrest is f=kx, p=f s, s=a 2

(1) Fill the graduated cylinder with an appropriate amount of water, and measure the volume as V1. Then take a flat-bottomed test tube filled with a small amount of sand and measure the mass m1. The tube is then placed into a graduated cylinder with water to float and the volume is v2.

Finally, change the mass of the loaded sand and make several measurements as described above.

2) The volume of water v1 of the tube and the mass of sand m1 of the volume of water after being placed in the tube v2

Collect fruits** almost.

(1) Fill the graduated cylinder with an appropriate amount of water, and measure the volume as V1. Then take a flat-bottomed test tube filled with a small amount of sand and measure the mass m1. The tube is then placed into a graduated cylinder with water to float and the volume is v2.

Finally, change the mass of the loaded sand and make several measurements as described above.

2) The volume of water v1 of the tube and the mass of sand m1 of the volume of water after being placed in the tube v2

Sample, don't understand to ask the teacher.

It's strange, I also graduated from junior high school, why don't I know how to write.

33 (9 points) In the experiment of measuring the electric power of a small bulb with a rated voltage, the circuit is shown in Figure A, (1) A student closes the switch after connecting the circuit correctly, and finds that the bulb does not light up, the ammeter has no indication number, and the voltage indication number is equal to the power supply voltage, and the fault may be the bulb open circuit.

2) After troubleshooting, when moving the slide p to a certain position, the voltage representation number is shown in Figure B, to measure the rated power of the small bulb, the slide p should be moved to the optional "a" or "b") end of the b.

3) move the slider p, write down the indication of multiple groups of corresponding voltmeters and ammeters, and draw the i u image shown in figure c, according to the image information, the rated power of the small bulb can be calculated is w. Do the math yourself.

4) If the ammeter is broken, there are a number of single-pole single-throw switches on the experimental table, and the resistance value is a fixed value resistor, which can be used, and the resistance of 5 should be selected to measure the rated power of the small bulb, please draw the circuit diagram, and write out the steps and expressions (not dismantling the circuit in the experimental measurement).

After a student "what is the relationship between the trunk current and the current of each branch in the parallel circuit", he imagined whether he could complete the experiment with only one ammeter and only one wire? (The current through the bulb is known to be about.) Can you confirm his assumption?

1) The equipment and quantity required ---

2) Experimental procedure: --

3) Please evaluate this improvement: --

Answer: Prepare a switch for a light bulb; 1A ammeter, 1 pcs; Conducting wire.

1. Connect a parallel circuit, install an ammeter in the trunk circuit, and install switches and bulbs in each branch.

2. Connect the power supply, connect each branch in turn, connect one branch at a time, and record the reading of the ammeter.

You can get: a light bulb --- current; Two bulbs --- current; Three bulbs --- currents.

3. The sum of the current of each branch in the parallel circuit is obtained.

While doing the experiment of "observing the boiling of water", A. Second. The students in Group C and Group C each chose one of the two sets of equipment to complete the experiment

Second. Although the two groups of students chose the same experimental setup, the time when the water began to boil was different, and the boiling image they drew is shown in Figure C: the reason for the difference between the two images A and B is that the water is different.

Answer 1 The quality of the water.

2 A seems to have no lid on the beaker b There is a lid on the beaker, so the pressure in the beaker is different.

Measure the gravity of that part of the nut.

The gravitational force of the vial is:

The buoyancy experienced by the vial.

Take out the nut and dry the water off the vial.

According to the conditions: g>f sink g has something to say on qq: 1219056654

The third question: the candle can be placed at a distance, usually about 10 times the focal length (the focal length for the experiment is about 5cm 30cm), so that it is about 3m, aim at the candle with a convex lens, put the light screen behind the lens, and move back and forth until the light screen becomes a clear image, at this time the distance from the convex lens to the light screen is equal to the focal length.

Principle: When you are much larger than the focal length, v f

Aim the candle with a convex lens, place a light screen behind the lens, and move it back and forth until the light screen forms a clear inverted image of the same size, at this time the distance from the convex lens to the light screen is equal to twice the focal length.

(3) Can be analyzed: can a match be used as a light source to measure the focal length of a convex lens?

The principle is that the wine bottle filled with water is like a convex lens, and when the object distance is less than the focal length, the convex lens becomes an upright magnified virtual image.