A wire of diameter mm and length 50.0 m has a measured resistance of 3 ohm. What

Question

A wire of diameter mm and length 50.0 m has a measured resistance of 3 ohm. What is the resistivity of the wire? What current in a copper wire with a cross-sectional area of 7 x 10^-7 m^2 would result in a drift speed equal to 5 x 10^-4 m/s? Take number of electrons per unit volume to be n = 8.4 x 10^28 m^-3. At 20 C, a carbon (alpha = -.5 x 10^-1) resistor in an electric circuit connected to a 7.0 V battery has a resistance of 253 ohm. What is the current in the circuit when the temperature of the carbon rises to 75 C?

Explanation / Answer

The values what you got are right, but the units what you have written are wrong

Electrical resistivity of the wire is given by

           p =RA/L

Givent that R =3ohms and L =50m and r =0.004m then area of the wire A =pir2 =3.14*(0.004)2 =5.024*10-5m2

Now we get   p =(3)(5.024*10-5)/50=0.30144*10-5 =3.0144*10-6ohm-m

2.

The current through the copper wire is given I =nAqVd = (8.4*1028)(7*10-7)(5*10-4)(1.6*10-19) =470.4*10-2A=4.704A

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.