Chapter 24 Practice Pr soln

# Chapter 24 Practice Pr soln - what we shall use to compute...

This preview shows pages 1–2. Sign up to view the full content.

pg 1 Chapter 24 Practice Pr soln: 21. I NTERPRET This problem is about applying Ohm’s law to find the resistivity of a rod. D EVELOP If the rod has a uniform current density and obeys Ohm’s law (Equations 24.4a and 4b), then its resistivity is 2 ( /4) / E E E d J I A I π ρ = = = E VALUATE Substituting the values given in the problem, we find the resistivity of the rod to be 2 2 2 6 ( /4) (1.4 V/m) (10 m) /4 2.20 10 m 50 A E d I - - = = = × Ω⋅ 23. I NTERPRET This problem involves using Ohm’s law to calculate the resistance of a heating coil. D EVELOP The macroscopic form the Ohm’s law is probably applicable to the heating coil, which is typically a coil of wire. Equation 24.5 gives / . R V I = E VALUATE Substituting the values given in the problem statement, we find the resistance to be 120 V 25 4.8 A V R I = = = 29. I NTERPRET This problem is about electric power of a motor, given the current drawn and the voltage across the terminals. D EVELOP Equation 24.7, , P IV = provides the connection between electric current, voltage and electric power. This equation is

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: what we shall use to compute the power P . E VALUATE Substituting the values given in the problem, we find the power consumption to be pg 2 (125 A)(11 V) 1.38 kW P IV = = = 47. I NTERPRET This problem compares resistances of wires made up of different materials. Ohm’s law is involved. D EVELOP The resistance of a uniform wire of Ohmic material is given by Equation 24.6: / . R L A ρ = Therefore, the resistance per unit length is 2 /4 R L A d π = = E VALUATE Equal values of / R L for copper and aluminum wires imply that 8 Cu Al Al Al 2 2 8 Cu Cu Cu Al 2.65 10 m = 1.26 1.68 10 m d d d d--× Ω⋅ = → = = × Ω⋅ where we have used Table 24.1 for resistivities. A SSESS Since 1/ 2 , d z the higher the resistivity, the greater the diameter of the wire....
View Full Document

{[ snackBarMessage ]}

### Page1 / 2

Chapter 24 Practice Pr soln - what we shall use to compute...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online