Relatives help.。。 A physics problem 10

1) Close S1 and S2, slide rheostat R3 short circuit, R1R2 in parallel, total resistance 1 R=1 R1+1 R2=1 6+1 12

r = 4 ohms. 2) Disconnect S1, close S2, slide rheostat R3 short circuit, and R2 open circuit, Q=I 2R1T 60=I 2x6x10

i=1a u=ir1=1x6=6v

3) Disconnect S1, S2, R1 and Sliding Rheostat R3 in series. For safety, the maximum current does not exceed , and the total resistance is not less than r=u i=6 ohms, and r3 is not less than 4 ohms.

The voltage does not exceed 3V, at this time, the voltage of R1 and R3 is equal to 3V, and the resistance is also equal, and the maximum of R3 does not exceed 10 ohms.

The R3 ranges from 4 ohms to 10 ohms.

1) r=(r1*r2) (r1+r2) Calculate the value yourself!

2) q(60j)=p*t

p=u 2 (square of voltage) r1 According to these two formulas, let's solve it!

3) I can tell you the equivalent circuit, R1 and R3 and the ammeter are connected in series with the voltmeter in parallel with (R3 and the ammeter), use the power supply voltage, ensure that the meter is not burned, please, I am in front of the computer, this can think so much.

I'll take a look, but it will take time.

When the bar magnet is close to the ring, the magnetic flux through the ring increases, because the ring is closed, the magnetic field of its induced current will hinder the increase of this magnetic flux, so the ring and the magnet are repulsive, that is, the ring will press down on the table, so that the pressure increases.

In addition, the ring has a tendency to expand. Because the magnetic inductance lines passing through the ring have two directions (inside and outside the magnet), the ring has a tendency to expand, in order to cancel out more magnetic inductance lines (i.e., the magnetic flux through the ring decreases), so as to hinder the increase of the magnetic flux passing through it.

Hello, according to Lenz's law, the two objects repel each other, then the pressure of the ring on the desktop increases, according to the increase or contraction, the magnet near the magnetic flux becomes larger, then there is a contraction tendency.

Hope this helps, o(o

Do it with a strong **.

The rationality of the two ropes is equal to the gravity and the opposite direction, so there are two ropes that are symmetrical, and the angle of the cd is also 30°

Size 40n

As can be seen from the figure, the angle between the three lines is 120 degrees, and AB is a rope, regardless of the friction of the pulley, the tension (tension) of the AB rope is the same, and the force analysis of the pulley can obtain: the tensile force of the CD rope to the pulley is 40N, and the direction is the opposite direction of the angular bisector of ADB.