Introduction to Electric Current

Introduction to Electric Current

• The topic is about electric current through conductors, specifically how electric charge flows through them.
• The concept builds upon the previous chapter on electrostatics.
• The chapter discusses the movement of charges, focusing on the concept of electric current.

Electric Current

• It is defined as the rate of flow of electric charge. Electric current is represented by the symbol "I" and measured in Amperes.
• The formula for electric current is: I = Q/t, where:
  • I = electric current
  • Q = total charge
  • t = time in seconds
• One Coulomb is equal to the amount of charge that flows through a conductor in one second when the current is one Ampere.

Drift Velocity

• The drift velocity of charge carriers in a conductor is the average velocity with which they move under the effect of an electric field
• In a metallic conductor, electrons are the charge carriers.
• Drift velocity can be calculated using the following formula: Vd = I/(neA), where
  • Vd = drift velocity
  • I = electric current
  • n =n =The term "free electrons per unit volume"
  • e = charge of an electron
  • A represents the cross-sectional area of a conductor,

Ohm's Law

• Ohm's Law states that the current flowing through a conductor is directly proportional to the potential difference (voltage) applied across its ends, given that the physical conditions (temperature, etc.) remain constant.
• Mathematically, Ohm's law is expressed as: V = IR, where
  • V = potential difference across the conductor
  • I = current flowing through the conductor
  • R = resistance of the conductor
• Resistance is a measure of the opposition to the flow of electric current.

Conductance

• Conductance is the reciprocal of resistance.
• It is a measure of how well a material can conduct electric current.
• The unit of conductance is Siemens (S).
• The formula for conductance is: G = 1/R, where
  • G = conductance
  • R = resistance

Non-Ohmic Devices

• Not all devices follow Ohm's law.
• Semiconductors are an example of a non-ohmic device that does not obey Ohm's Law.
• Semiconductors exhibit a nonlinear relationship between voltage and current because they show a resistance that depends on the applied voltage.

Limitations of Ohm's Law

• Ohm's Law is not universally applicable, particularly in cases where the physical conditions of the conductor change significantly.
• Joule heating, caused by resistance, can affect the temperature of the conductor, thereby altering its resistance and the validity of Ohm's Law.
• Another limitation of Ohm's Law is that it doesn't apply to devices like semiconductors where the relationship between voltage and current is not linear.

Key Takeaways

• Understanding the concepts of electric current, drift velocity, and Ohm's Law is crucial for comprehending electrical circuits.
• Ohm's Law is fundamental to the study of electricity and provides a simple relationship between voltage, current, and resistance in many circuits.
• It is important to remember that Ohm's law has limitations and might not apply in all situations.

Electric Current

• Electric current is the rate of flow of electric charge.
• Current is measured in Amperes (A).
• The formula for current is: I = Q/t, where I is current, Q is charge, and t is time.
• One Coulomb of charge is the amount that flows through a conductor in one second when the current is one Ampere.

Drift Velocity

• Drift velocity is the average velocity of charge carriers in a conductor when moving under the influence of an electric field.
• In metallic conductors, electrons are the charge carriers.
• Drift velocity is calculated using the formula: Vd = I/(neA), where Vd is drift velocity, I is current, n is the number of free electrons per unit volume, e is the charge of an electron, and A is the cross-sectional area of the conductor.

Ohm's Law

• Ohm's Law states that the current flowing through a conductor is directly proportional to the potential difference (voltage) applied across its ends, provided physical conditions like temperature remain constant.
• Mathematically, Ohm's Law is expressed as: V = IR, where V is voltage, I is current, and R is resistance.
• Resistance is the opposition to the flow of electric current.

Conductance

• Conductance is the reciprocal of resistance.
• It measures how well a material conducts electric current.
• The unit of conductance is Siemens (S).
• The formula for conductance is: G = 1/R, where G is conductance and R is resistance.

Non-Ohmic Devices

• Not all devices follow Ohm's Law.
• Semiconductors are an example of a non-ohmic device.
• Semiconductors have a nonlinear relationship between voltage and current, meaning their resistance changes with applied voltage.

Limitations of Ohm's Law

• Ohm's Law is not universally applicable.
• Joule heating, caused by resistance, can change the temperature of a conductor, affecting its resistance and the validity of Ohm's Law.
• Ohm's Law doesn't apply to devices like semiconductors where the relationship between voltage and current is not linear.

This quiz covers the fundamentals of electric current, focusing on how electric charges flow through conductors. Key concepts include the definition of electric current, its measurement in Amperes, and the crucial formula I = Q/t. Additionally, the quiz explores drift velocity and the behavior of charge carriers in metallic conductors.