 Lecture in Electric Currents

(Last Updated On: December 13, 2017)

Lesson Objectives – the students should be able to:

• Explain how a simple battery can produce an electrical current.
• Define current, ampere, emf, voltage, resistance, resistivity, and temperature coefficient of resistance.
• Write the symbols used for electromotive force, electric current, resistance, resistivity, temperature coefficient of resistance and power and state the unit associated with each quantity.
• Distinguish between a) conventional current and electron current and b) direct current and alternating current.
• Know the symbols used to represent a source of emf, resistor, voltmeter, and ammeter and how to interpret a simple circuit diagram.
• Given the length, cross sectional area, resistivity, and temperature coefficient of resistance, determine a wire’s resistance at room temperature and some higher or lower temperature.
• Solve simple dc circuit problems using Ohm’s law.
• Use the equations for electric power to determine the power and energy dissipated in a resistor and calculate the cost of this energy to the consumer.
• Distinguish between the rms and peak values for current and voltage and apply these concepts in solving problems involving a simple ac circuit.
• Compute Power in Household Circuits
• Understand the Microscopic View of Electric Current
• Learn the concept of Superconductivity
• Could understand the Electrical Conduction in the Human Nervous System

Summary of Chapter 18

• A battery is a source of constant potential difference.
• Electric current is the rate of flow of electric charge.
• Conventional current is in the direction that positive charge would flow.
• Resistance is the ratio of voltage to current:
• Ohmic materials have constant resistance, independent of voltage.
• Resistance is determined by shape and material:
• ρ is the resistivity.
• Power in an electric circuit:
• Direct current is constant
• Alternating current varies sinusoidally
• The average (rms) current and voltage:
• Relation between drift speed and current:

Units of Chapter 18 – Keywords

• The Electric Battery
• Electric Current
• Ohm’s Law: Resistance and Resistors
• Resistivity
• Electric Power
• Power in Household Circuits
• Alternating Current
• Microscopic View of Electric Current
• Superconductivity
• Electrical Conduction in the Human Nervous System
• Volta
• electrolyte