If the mass of a bundle of copper wires is 4.45kg and the wire specification is 2mm, what is the length of the bundle

If the mass of a bundle of copper wires is 4.45kg and the wire specification is 2mm, what is the length of the bundle

Specific gravity of copper wire: 8.9g/cm ^ 3
4.45kg copper conductor is equal to 4450g. Volume is equal to 4450 / 8.9 = 500 cubic centimeter = 0.0005 cubic meter
The length of copper wire is equal to volume divided by sectional area = 0.0005/0.00000 2 = 250 M
The uniform resistance wire with total resistance of 2R is welded into a ring with radius of a and fixed horizontally in a uniform magnetic field with vertical and downward magnetic induction of B. as shown in the figure, a metal bar Mn with length of 2a, resistance equal to 2R and uniform thickness is placed on the ring and keeps good contact with the ring all the time. When the metal bar moves to the right at a constant speed V and passes through the distance o from the ring center, the following formula is obtained
(1) The magnitude and direction of the current on the rod and the voltage U
(2) The total thermal power consumed on the ring and on the metal bar
Please explain the analysis of the current on the rod and the ring
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Because I can't see your picture, I can only calculate the value for you
(1) Voltage value: u = b * L * V L = 2A, so u = 2abv
The direction of current should be determined by right hand rule
Current value: I = u / R; r = 2R + 0.5r = 2.5R;
So I = 4abv / 5R
（2）P=U*I=8（aBV）²/5R
The resistance of a conductor is 6 ohm, and the voltage at both ends is 12 V, which is the current and power it passes
I = u / r = 12V / 6ohm = 2A
p=UI=12V×2A=24w
I=U/R =2A P=UI=24W
The quality of a copper plate is changed by (a) rolling the copper plate into thin copper plate (b) melting the copper plate into copper water (c) heating the copper plate to 800 ℃
(D) File the copper into a square
The answer is D, but C can also be selected. When copper is heated in the air, copper reacts with oxygen to form copper oxide, and the quality of copper plate will also increase!
ABC does not change the quality, D copper file into a square quality reduction
(D) File the copper into a square
Because some copper was filed away.
The other answers B and C do not indicate under what conditions, if not, whether chemical reactions have been carried out to change the quality, so they are not selected. A is just a change in shape, so it's not.
23. Rectangular wire frame ABCD with resistance R, side length AB = L, ad = h, mass m, falls freely from a certain height,
For what? For velocity, displacement, using kinematic formulas
Calculate the voltage and current at both ends of the resistance. Insufficient conditions, no directional magnetic field
S = AB for rectangular area
If the condition complement, welcome to ask again
What is the solution?
In a circuit, the resistance is increased by 4 ohm and the current is reduced to half of the original. If the supply voltage remains unchanged, what is the resistance in the original circuit?
If I / R is set to 2, then I / R is set to 2
R =U/I
R+4=U/(I/2)
R + 4 = 2 * U / I
Substitute the U / I of the first formula into the last one
R+4=2*R
The solution is r = 4
So the source resistance is 4 ohm
4 ohm.
4ou
There is a bundle of aluminum wire. Its mass is 16.2kg. Its cross-sectional area is 2mm. Find the length
This is the problem
It should be about 3000 meters, 16200 / 5.4 = 3000, 2.7 is the density of 2 square mm, X1000 mm = 2cm & sup3; x2.7 = 5.4
Resistance R frame ABCD, ab = L, ad = h, mass m, free fall, through uniform magnetic field, magnetic field perpendicular to the paper face inward, magnetic field width h, frame with constant speed magnetic field
Seeking Joule heat
If the box passes through the magnetic field at a constant speed, it means that its kinetic energy does not change. Then where is the potential energy when it falls? It turns into heat! That's the answer!
The reduced potential energy is e = mg * 2H (in which there are 2h, which is the penetration and exit, so it is 2H), which is the answer!
Understand?
If two resistors with resistance values of 4 Ω and 6 Ω are connected in series to a power supply with constant voltage, the current in the circuit is 1.2A; if they are connected in parallel to the same power supply, what is the current in the trunk circuit?
U = I (R1 + R2) = 1.2A × (4 Ω + 6 Ω) = 12vr and = 11r1 + & nbsp; 1r2 = & nbsp; & nbsp; 114 Ω + 16 Ω = 2.4 Ω I and = ur and & nbsp; = 12v2.4 Ω = 5A A: the current in the trunk road is 5A
How much current can a square copper wire produce?
How much current a conductor can pass is not a fixed value. It is called current density in the specialty. It depends on the allowable temperature rise and line voltage drop. Generally speaking, the shorter and better heat dissipation conductor mainly considers the temperature rise and can choose the higher current density. The voltage drop should be considered for the longer wire (hundreds of meters), and the lower current density is often selected. If the maximum allowable current is used, the higher current density is selected, Not to mention the temperature rise, the terminal voltage is not enough
The safe current carrying capacity of national standard 1 square millimeter bv conductor (ambient temperature 35 ℃, core temperature 80 ℃), single overhead 17a, two through pipe 15a, three through pipe 12a, four through pipe 10A. However, such a large current density is rarely used in practice, and 5A ~ 10A is commonly used