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Chapter 26

Current and Resistance

Electrical Current
Electrical Current
Electrical current is defined as the rate at which charge flows. When there is a large current present, such as that used to run a refrigerator, a large ...
Drift Velocity
Drift Velocity
The high speed of electrical signals results from the fact that the force between charges acts rapidly at a distance. Thus, when a free charge is forced ...
Current Density
Current Density
The total amount of current flowing through one unit value of a cross-sectional area is referred to as current density. If the current flow is uniform, ...
Resistivity
Resistivity
When a voltage is applied to a conductor, an electrical field is generated, and charges in the conductor feel the force due to the electrical field. The ...
Resistance
Resistance
When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...
Ohm's Law
Ohm's Law
Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm’s law. The current that flows ...
Non-ohmic Devices
Non-ohmic Devices
In most substances, the current flow is proportional to the voltage applied to it. A simple relationship between the values of current, voltage, and ...
Electrical Power
Electrical Power
Electric power is the product of current and voltage, represented in units of joules per second, or watts. For example, cars often have one or more ...
Electrical Energy
Electrical Energy
Using electric appliances for a longer period of time consumes more electrical energy and results in a higher electric bill. The energy produced by the ...
Continuity Equation
Continuity Equation
The total amount of current flowing per unit cross-sectional area is called the current density. Hence, the current passing through a cross-sectional area ...
Boundary Conditions for Current Density
Boundary Conditions for Current Density
Current density becomes discontinuous across an interface of materials with different electrical conductivities. The normal component of the current ...
Electrical Conductivity
Electrical Conductivity
In perfect conductors, the electric field inside is always zero due to the abundance of free electrons, which nullify any field by flowing. As a result, ...
Theory of Metallic Conduction
Theory of Metallic Conduction
The conduction of free electrons inside a conductor is best described by quantum mechanics. However, a classical model makes predictions close to the ...
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