# Physics

posted by .

(1) 45 micro coulombs of charge is passed through a wire in 35 seconds. How many electrons does this represent? What is the current in the wire?

(2) A piece of copper wire has a resistance of 5 Ohms at 20 degrees celsius. If another piece of copper wire at 0 degrees celsius is 3 times as long and has a cross sectional area that's twice as big, what will its resistance be?

• Physics -

(1) The current (in Amperes) is the charge divided by the time. Divide that once again by the electron charge to get the number on electrons per second.

(2) Resistance is proportional to length and inversely proportional to the wire's cross sectional area. Knowing that, what do you think the answer is?

For highest accuracy, you will have to account for the chance in resistivity with temperature. which is quite small over a range from 0 to 20 C.

## Similar Questions

1. ### physics

a very thin piece of copper wire has an electrical resistance of 20,000 Ohms. You connect its ends to a regular 2.0 Volt battery. How much power does it draw?
2. ### physics

a very thin piece of copper wire has an electrical resistance of 20,000 Ohms. You connect its ends to a regular 2.0 Volt battery. How much power does it draw?
3. ### physics

a very thin piece of copper wire has an electrical resistance of 20,000 Ohms. You connect its ends to a regular 2.0 Volt battery. How much power does it draw?
4. ### physics

A copper wire has a circular cross section with a radius of 3.75 mm. If the wire carries a current of 4.00 A, find the drift speed of the electrons in the wire. (Assume the density of charge carriers (electrons) in a copper wire is …
5. ### physics

A copper wire has a circular cross section with a radius of 3.75 mm. If the wire carries a current of 4.00 A, find the drift speed of the electrons in the wire. (Assume the density of charge carriers (electrons) in a copper wire is …
6. ### physics

copper has 8.5 x 10^28 electrons per cubic meter. (a) how many electrons are there in 30 cm length a 12 gauge copper wire (diameter 2.05 mm)?
7. ### college physics

A 4m long copper wire has a diameter of 2mm and carries a current of 10A. Determine the ff: a. current density in the wire b. electric field c. potential difference between the ends of the wire d. resistance of the wire
8. ### physics

Consider two copper wires with the same cross-sectional area. Wire A is twice as long as wire B. How do the resistivities and resistances of the two wires compare?
9. ### As physics

Please help and do it step by step all parts of questions and use: T = time(s) I=current (amps) Q=net charge on object (Coulombs) N=no electrons (and write if added or removed from object and how) E=elementary charge A piece of fuse …
10. ### physics As

Please help and do it step by step all parts of questions and use: T = time(s) I=current (amps) Q=net charge on object (Coulombs) N=no electrons (and write if added or removed from object and how) E=elementary charge A piece of fuse …

More Similar Questions