Home » Study Help » GENERAL PHYSICS 242 Help- mastering physics – 2018 Physics Course – University Physics with Modern Physics, 14e

GENERAL PHYSICS 242 Help- mastering physics – 2018 Physics Course – University Physics with Modern Physics, 14e

Hi students!

If you are worried about your 2018 Physics Course (mastering physics). And if you are searching a tutor for GENERAL PHYSICS 242 – mastering physics Course. Then you can contact me. We are sharing a link of mastering physics Help- GENERAL PHYSICS 242 Chapter 25 for Demo.

Contact Us: +92 333 2487535 (WhatsApp)

Download:     GENERAL PHYSICS 242-GENERAL PHYSICS 242 Chapter 25

Overview of Chapter 25:

Introduction to Electric Current

Learning Goal:

To understand the nature of electric current and the conditions under which it exists.

Electric current is defined as the motion of electric charge through a conductor. Conductors are materials that contain movable charged particles. In metals, the most commonly used conductors, such charged particles are electrons. The more electrons that pass through a cross section of a conductor per second, the greater the current. The conventional definition of current is

I=QtotalΔt,

where I is the current in a conductor and Qtotal is the total charge passing through a cross section of the conductor during the time interval Δt.

The motion of free electrons in metals not subjected to an electric field is random: Even though the electrons move fairly rapidly, the net result of such motion is that Qtotal=0 (i.e., equal numbers of electrons pass through the cross section in opposite directions). However, when an electric field is imposed, the electrons continue in their random motion, but in addition, they tend to move in the direction of the force applied by the electric field.

In summary, the two conditions for electric current in a material are the presence of movable charged particles in the material and the presence of an electric field.

Quantitatively, the motion of electrons under the influence of an electric field is described by the drift speed, which tends to be much smaller than the speed of the random motion of the electrons. The number of electrons passing through a cross section of a conductor depends on the drift speed (which, in turn, is determined by both the microscopic structure of the material and the electric field) and the cross-sectional area of the conductor.

In this problem, you will be offered several conceptual questions that will help you gain an understanding of electric current in metals.

Part A

You are presented with several long cylinders made of different materials. Which of them are likely to be good conductors of electric current?

Part B

Part C

Part D

You are presented with several wires made of the same conducting material. The radius and drift speed are given for each wire in terms of some unknown units rand v. Rank the wires in order of decreasing electron current.

Part E

Q.2:

At room temperature, what is the strength of the electric field in a 12-gauge copper wire (diameter 2.05 mm ) that is needed to cause a 3.90 A current to flow?

Q.3:

What diameter must a copper wire have if its resistance is to be the same as that of an equal length of aluminum wire with diameter 2.44 mm ?

Q.4:

A carbon resistor is to be used as a thermometer. On a winter day when the temperature is 4.0 C, the resistance of the carbon resistor is 217.6 Ω .
==>

To learn to apply the concept of current density and Kirchhoff’s junction rule.
Consider a junction of five wires, as shown in the figure. The arrows indicate the direction of current flow.
The information about the magnitudes of the current density and the diameters for wires 1, 2, 3, and 4 is given in the table. Some of the values are unknown.

Wire Current density (A/mm2) Diameter (mm) Total Current (A)
1 1.6 2.0 ???
2 ??? 3.0 2.0
3 3.0 1.1 ???
4 0.8 ??? 4.0
Find the current I5 in wire 5.
==>

Exercise 25.1 – Enhanced – with Solution

You may want to review (Pages 817 – 820) .

For related problemsolving tips and strategies, you may want to view a Video Tutor Solution of Current density and drift velocity in a wire.

Part A

==>

Exercise 25.7 – Enhanced – with Solution

The current in a wire varies with time according to the relation I=55A(0.65A/s2)t2.You may want to review (Pages 817 – 820) .

For related problem-solving tips and strategies, you may want to view a Video Tutor Solution of Current density and drift velocity in a wire.

Part A

How many coulombs of charge pass a cross section of the wire in the time interval between t=0 and t = 7.5 s ?

Part B

What constant current would transport the same charge in the same time interval?

Exercise 25.10

Part A

At room temperature, what is the strength of the electric field in a 12-gauge copper wire (diameter 2.05 mm ) that is needed to cause a 3.90 A current to flow?

Part B

What field would be needed if the wire were made of silver instead?

Exercise 25.18

Part A

What diameter must a copper wire have if its resistance is to be the same as that of an equal length of aluminum wire with diameter 2.44 mm ?

Exercise 25.24

A carbon resistor is to be used as a thermometer. On a winter day when the temperature is 4.0 C, the resistance of the carbon resistor is 217.6 Ω .

Part A

About Farhan

Leave a Reply

Your email address will not be published. Required fields are marked *

*

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: