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Questions and Answers

What is the significance of selecting materials like manganin and constantan for wire bound resistors?

These materials have resistivities that are relatively insensitive to temperature, ensuring consistent resistance across varying conditions.

Explain how the colour code works for identifying the value of carbon resistors.

The first two colour bands represent the first two significant figures of resistance, the third indicates the decimal multiplier, and the last band represents tolerance.

How does Ohm's Law relate to the functioning of wire bound resistors?

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, which applies to wire bound resistors in providing defined resistance.

What defines the tolerance of a resistor and why is it important?

Tolerance indicates the possible variation in resistance, typically as a percentage, allowing for better accuracy in circuit design and application. Signup and view all the answers

Describe the role of current density in the context of resistors.

Current density refers to the amount of current per unit area of the conductor, influencing the heating effect in resistors due to resistive losses. Signup and view all the answers

How does the drift of electrons contribute to the resistance observed in wire bound resistors?

The drift of electrons through the resistor material encounters collisions with atoms, resulting in resistance as energy is dissipated as heat. Signup and view all the answers

What relationship exists between the electric field and potential difference in resistors?

The electric field within a resistor creates a potential difference that drives the flow of current, as described by Ohm's Law. Signup and view all the answers

State Kirchhoff's law as it applies to circuits containing resistors.

Kirchhoff's law states that the total current entering a junction equals the total current leaving the junction, ensuring circuit continuity. Signup and view all the answers

What is the definition of mobility in the context of drift velocity and electric field?

Mobility (µ) is defined as the magnitude of the drift velocity (|vd|) per unit electric field (E), expressed as µ = |vd| / E. Signup and view all the answers

What are the SI units of mobility and how do they compare to practical units?

The SI unit of mobility is m²/Vs, which is equivalent to 10⁴ cm²/Vs in practical units. Signup and view all the answers

Identify a major limitation of Ohm's Law related to the relationship between voltage and current.

One major limitation is that voltage (V) may cease to be proportional to current (I) in certain materials, resulting in nonlinear V-I characteristics. Signup and view all the answers

In what way can the relationship between voltage and current be dependent on the sign of voltage?

The relationship can depend on the sign such that reversing the direction of voltage (while keeping its magnitude fixed) does not yield the same magnitude of current in the opposite direction. Signup and view all the answers

What characteristic of GaAs indicates that the relation between voltage and current is not unique?

GaAs exhibits behavior where there can be more than one value of voltage for the same current, indicating a non-unique relationship. Signup and view all the answers

What is the relationship defined by Ohm's Law?

Ohm's Law states that the current $I$ through a conductor between two points is directly proportional to the voltage $V$ across the two points and inversely proportional to the resistance $R$, expressed as $I = \frac{V}{R}$. Signup and view all the answers

How does the average collision time (τ) relate to drift velocity in determining mobility?

The drift velocity (vd) is proportional to the average collision time (τ) and the electric field (E) in the equation µ = e τ / (m E). Signup and view all the answers

How does the current density relate to total current in a conductor?

Current density $J$ is defined as the amount of current $I$ flowing per unit area $A$, expressed as $J = \frac{I}{A}$. Signup and view all the answers

What causes the drift of electrons in a conductor?

The drift of electrons in a conductor is primarily caused by the application of an electric field, which creates a force on the free electrons, causing them to move in a particular direction. Signup and view all the answers

What is the significance of drift velocity in the context of current flow in conductors?

Drift velocity represents the average velocity of charge carriers (like electrons) in a conductor due to an electric field, and it is essential for calculating current flow. Signup and view all the answers

Explain why certain materials and devices that do not obey Ohm's Law are still commonly used in electronic circuits.

Materials and devices that do not follow Ohm's Law can offer unique electrical characteristics, such as rectification in diodes, making them valuable in various applications. Signup and view all the answers

Define the relationship between electric field and potential difference.

The electric field $E$ between two points in a circuit is related to the potential difference $V$ as $E = -\frac{dV}{dx}$, with $dx$ being the distance between the points. Signup and view all the answers

What are Kirchhoff’s laws and their purpose in analyzing circuits?

Kirchhoff's laws include the Junction Rule, which states that the total current entering a junction equals the total current leaving, and the Loop Rule, which states that the sum of the voltage differences around any closed loop is zero. Signup and view all the answers

Explain the term mobility in the context of charge carriers in a conductor.

Mobility refers to how quickly a charge carrier (like an electron) can move through a material under the influence of an electric field, typically expressed as $\mu = \frac{v_d}{E}$, where $v_d$ is the drift velocity and $E$ is the electric field strength. Signup and view all the answers

What does the color coding on a carbon resistor indicate?

The color bands on a carbon resistor indicate its resistance value and tolerance, with each color representing a specific digit or multiplier according to a standardized coding system. Signup and view all the answers

How can internal resistance affect the performance of a cell in parallel with other cells?

Internal resistance can lead to power losses and reduce the effective emf of a cell when connected in parallel, as it adds to the overall resistance and affects the current distribution. Signup and view all the answers

Flashcards

Wirewound Resistors Material

Wirewound resistors are made from alloys like manganin, constantan, nichrome, with resistivities that don't change much with temperature.

Wirewound Resistor Range

Wirewound resistors typically have values from a small fraction of an ohm to a few hundred ohms.