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Questions and Answers
What is the drift speed of electrons in copper as calculated in the document?
What is the drift speed of electrons in copper as calculated in the document?
- $5.57 \times 10^{-5}$ m/s (correct)
- $3.45 \times 10^{-5}$ m/s
- $4.75 \times 10^{-5}$ m/s
- $6.29 \times 10^{-5}$ m/s
What is the expression for current density in terms of current and cross-sectional area?
What is the expression for current density in terms of current and cross-sectional area?
- $J = \frac{I}{A}$ (correct)
- $J = I + A$
- $J = \frac{I}{2A}$
- $J = I \times A$
At time $t = 1$ s, what is the instantaneous current as given in the document?
At time $t = 1$ s, what is the instantaneous current as given in the document?
- 5 A
- 12 A
- 10 A
- 17 A (correct)
What is the calculated current density for a current of 17 A and cross-sectional area of $2 \times 10^{-4}$ m²?
What is the calculated current density for a current of 17 A and cross-sectional area of $2 \times 10^{-4}$ m²?
From Ohm's law, the expression for current can be defined as which of the following?
From Ohm's law, the expression for current can be defined as which of the following?
Given the resistivity of tungsten, what is the resistance calculated for a specific configuration?
Given the resistivity of tungsten, what is the resistance calculated for a specific configuration?
What is the role of drift speed in the conduction of electricity?
What is the role of drift speed in the conduction of electricity?
What physical quantity does the symbol 𝜌 represent in the resistance calculations?
What physical quantity does the symbol 𝜌 represent in the resistance calculations?
What happens to the resistivity of a conductor as temperature increases?
What happens to the resistivity of a conductor as temperature increases?
What does the temperature coefficient of resistivity (α) indicate?
What does the temperature coefficient of resistivity (α) indicate?
Which equation represents the relationship of resistance and temperature?
Which equation represents the relationship of resistance and temperature?
In the equation $I = \frac{\Delta V}{R}$, what does I represent?
In the equation $I = \frac{\Delta V}{R}$, what does I represent?
What occurs to the resistivity of semiconductors with temperature according to the discussion?
What occurs to the resistivity of semiconductors with temperature according to the discussion?
What characterizes the nonlinear region of resistivity in metals at low temperatures?
What characterizes the nonlinear region of resistivity in metals at low temperatures?
What does the equation $\rho = \rho_0 (1 + \alpha (T - T_0))$ describe?
What does the equation $\rho = \rho_0 (1 + \alpha (T - T_0))$ describe?
What process does electrical power describe in a circuit?
What process does electrical power describe in a circuit?
What is the formula used to calculate the resistance of a material based on resistivity?
What is the formula used to calculate the resistance of a material based on resistivity?
Given the resistivity of aluminum (𝜌𝐴𝑙) is $2.82 × 10^{-8} Ω m$, what is its unit in the International System of Units?
Given the resistivity of aluminum (𝜌𝐴𝑙) is $2.82 × 10^{-8} Ω m$, what is its unit in the International System of Units?
What is the value of the fractional change in resistance (f) when α = $5 × 10^{-3} ℃^{-1}$, T = 50, and T0 = 25?
What is the value of the fractional change in resistance (f) when α = $5 × 10^{-3} ℃^{-1}$, T = 50, and T0 = 25?
If the resistance of a silver wire is calculated using the given α for silver as $3.8 × 10^{-3} ℃^{-1}$, what is the resistance when R0 is 6 Ω and the temperature changes from 20°C to 34°C?
If the resistance of a silver wire is calculated using the given α for silver as $3.8 × 10^{-3} ℃^{-1}$, what is the resistance when R0 is 6 Ω and the temperature changes from 20°C to 34°C?
What does the variable α represent in the resistance equation?
What does the variable α represent in the resistance equation?
How is current (I) found using power (P) and voltage (∆V) in a resistor?
How is current (I) found using power (P) and voltage (∆V) in a resistor?
What is the equivalent resistance (R) if the power (P) is 120 Watts and the voltage (∆V) is 1000 Volts?
What is the equivalent resistance (R) if the power (P) is 120 Watts and the voltage (∆V) is 1000 Volts?
What relationship does decreasing the area (A) of a material have on its resistance (R) when the resistivity and length remain constant?
What relationship does decreasing the area (A) of a material have on its resistance (R) when the resistivity and length remain constant?
What is the effect of temperature on the resistance of a conductor if the temperature coefficient (α) is positive?
What is the effect of temperature on the resistance of a conductor if the temperature coefficient (α) is positive?
Which equation accurately defines the change in resistance (R) considering initial resistance (R0), temperature change (T - T0), and temperature coefficient (α)?
Which equation accurately defines the change in resistance (R) considering initial resistance (R0), temperature change (T - T0), and temperature coefficient (α)?
Flashcards
Resistance of aluminum
Resistance of aluminum
The resistance of aluminum is 2.82 x 10^-8 Ω.m
Resistance of copper
Resistance of copper
The resistance of copper is 1.7 x 10^-8 Ω.m
Resistance formula
Resistance formula
Resistance (R) = (resistivity (ρ) * length (l)) / area (A)
Relationship between aluminum and copper radius
Relationship between aluminum and copper radius
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Thermal resistance coefficient of iron
Thermal resistance coefficient of iron
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Resistance change with temperature formula
Resistance change with temperature formula
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Fractional resistance change
Fractional resistance change
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Resistance of silver coefficient
Resistance of silver coefficient
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Power in Resistor Equation
Power in Resistor Equation
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Resistance from Power Equation
Resistance from Power Equation
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Drift speed (vd)
Drift speed (vd)
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Current in a conductor (I)
Current in a conductor (I)
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Current density (J)
Current density (J)
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Resistivity (ρ)
Resistivity (ρ)
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Resistance (R)
Resistance (R)
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Ohm's Law
Ohm's Law
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Instantaneous current
Instantaneous current
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Cross-sectional area (A)
Cross-sectional area (A)
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Resistivity and Temperature
Resistivity and Temperature
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Resistivity Equation
Resistivity Equation
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Temperature Coefficient of Resistivity
Temperature Coefficient of Resistivity
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Semiconductors and Resistivity
Semiconductors and Resistivity
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Resistance and Temperature Relationship
Resistance and Temperature Relationship
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Power in a Circuit
Power in a Circuit
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Electrical Power Equation
Electrical Power Equation
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Study Notes
Chapter 27: Current and Resistance
- This chapter covers electric current, resistance, resistance and temperature, and electrical power.
27.1 Electric Current
- Charges moving perpendicular to a surface of area A create an average current.
- Average current (Iavg) = ΔQ/Δt, where ΔQ is the charge passing through A in time Δt.
- Instantaneous current (I) = dQ/dt, the rate of change of charge flow.
- SI unit of current is the ampere (A), 1 A = 1 C/s.
- Conventional current direction is the direction positive charges would flow.
- In conductors, current is due to electron motion, opposite to electron flow.
- In gases and electrolytes, both positive and negative ions carry charge.
27.2 Resistance
- Current density (J) = I/A, the current per unit area, a uniform current.
- Electric field (E) exists in a conductor whenever there's a potential difference across it.
- Ohm's Law: For many materials (especially metals), the ratio of current density to electric field (σ) is constant. J = σE.
- Conductivity (σ) is a material property of Ohmic materials.
- Non-ohmic materials do not obey Ohm's Law.
- Resistance (R) = pl/A, where p is resistivity, l is the length, and A is the cross-sectional area.
- SI unit for R is Ohm (Ω)
27.4 Resistance and Temperature
- Resistivity (p) varies with temperature in most materials.
- ρ = ρ0[1 + α(T - T0)], where ρ0 is resistivity at reference temperature T0 (often 20°C) and α is the temperature coefficient of resistivity.
- Ideal conductors have zero resistivity.
- Ideal insulators have infinite resistivity.
27.6 Electrical Power
- Power is the rate of energy transfer.
- P = IΔV = I2R = ΔV2/R, where P is power, I is current, ΔV is potential difference, and R is resistance.
- SI unit for power is Watt (W), 1 W = 1 J/s.
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