Inductance - AP Physics C: Electricity and Magnetism
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How does a change in current affect the induced emf in an inductor?
How does a change in current affect the induced emf in an inductor?
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Emf is proportional to rate of change. Faster current changes produce larger opposing EMF.
Emf is proportional to rate of change. Faster current changes produce larger opposing EMF.
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State the formula for self-induced emf.
State the formula for self-induced emf.
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$\text{emf} = -L \frac{dI}{dt}$. Negative sign shows opposition to current change (Lenz's law).
$\text{emf} = -L \frac{dI}{dt}$. Negative sign shows opposition to current change (Lenz's law).
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Which physical quantity opposes changes in current in an inductor?
Which physical quantity opposes changes in current in an inductor?
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Induced EMF. Back EMF opposes changes per Lenz's law.
Induced EMF. Back EMF opposes changes per Lenz's law.
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Identify the factor that does not affect inductance.
Identify the factor that does not affect inductance.
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Temperature. Inductance depends on physical geometry, not thermal properties.
Temperature. Inductance depends on physical geometry, not thermal properties.
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What is the role of permeability in inductance?
What is the role of permeability in inductance?
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Higher permeability increases inductance. Higher permeability strengthens magnetic field in core.
Higher permeability increases inductance. Higher permeability strengthens magnetic field in core.
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What does the negative sign in $-\frac{dI}{dt}$ indicate in Faraday's Law?
What does the negative sign in $-\frac{dI}{dt}$ indicate in Faraday's Law?
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Direction opposes change. Indicates EMF opposes the current change (Lenz's law).
Direction opposes change. Indicates EMF opposes the current change (Lenz's law).
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Describe the effect of core saturation on inductance.
Describe the effect of core saturation on inductance.
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Reduces inductance. Saturated core cannot increase flux despite more current.
Reduces inductance. Saturated core cannot increase flux despite more current.
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What happens to inductance if the coil length is halved?
What happens to inductance if the coil length is halved?
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Inductance doubles. Length appears in denominator, so halving doubles inductance.
Inductance doubles. Length appears in denominator, so halving doubles inductance.
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Calculate the energy if L=0.8 H and I=5 A.
Calculate the energy if L=0.8 H and I=5 A.
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$E = 10 \text{ J}$. Using $E = \frac{1}{2} \times 0.8 \times 5^2 = 10$ J.
$E = 10 \text{ J}$. Using $E = \frac{1}{2} \times 0.8 \times 5^2 = 10$ J.
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Identify the symbol commonly used for inductance in equations.
Identify the symbol commonly used for inductance in equations.
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$L$. Standard notation in electromagnetic equations.
$L$. Standard notation in electromagnetic equations.
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How does increasing the number of turns in a coil affect its inductance?
How does increasing the number of turns in a coil affect its inductance?
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Increases inductance. More turns create stronger magnetic field and flux linkage.
Increases inductance. More turns create stronger magnetic field and flux linkage.
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State the unit of mutual inductance.
State the unit of mutual inductance.
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Henry (H). Same unit as self-inductance, both measure flux-current ratio.
Henry (H). Same unit as self-inductance, both measure flux-current ratio.
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Calculate the emf induced if L=2 H and $\frac{dI}{dt}=3 A/s$.
Calculate the emf induced if L=2 H and $\frac{dI}{dt}=3 A/s$.
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$\text{emf} = -6 \text{ V}$. From $\text{emf} = -L \frac{dI}{dt} = -2 \times 3$.
$\text{emf} = -6 \text{ V}$. From $\text{emf} = -L \frac{dI}{dt} = -2 \times 3$.
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What is the symbol for mutual inductance in equations?
What is the symbol for mutual inductance in equations?
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$M$. Standard symbol for mutual inductance coefficient.
$M$. Standard symbol for mutual inductance coefficient.
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What is the relationship between inductance and magnetic flux?
What is the relationship between inductance and magnetic flux?
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$L = \frac{\text{N} \times \text{Φ}}{\text{I}}$. Inductance equals flux linkage divided by current.
$L = \frac{\text{N} \times \text{Φ}}{\text{I}}$. Inductance equals flux linkage divided by current.
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What is the role of permeability in inductance?
What is the role of permeability in inductance?
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Higher permeability increases inductance. Higher permeability strengthens magnetic field in core.
Higher permeability increases inductance. Higher permeability strengthens magnetic field in core.
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How is inductance related to coil area?
How is inductance related to coil area?
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Larger area increases inductance. Larger area captures more magnetic flux lines.
Larger area increases inductance. Larger area captures more magnetic flux lines.
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What type of inductance occurs in a single circuit?
What type of inductance occurs in a single circuit?
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Self-inductance. Single coil inducing EMF in itself.
Self-inductance. Single coil inducing EMF in itself.
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State the formula for inductance of a solenoid.
State the formula for inductance of a solenoid.
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$L = \frac{\text{N}^2 \times \text{A} \times \text{μ}}{\text{l}}$. Relates turns squared, area, and permeability to length.
$L = \frac{\text{N}^2 \times \text{A} \times \text{μ}}{\text{l}}$. Relates turns squared, area, and permeability to length.
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What is the effect of decreasing the number of turns on a coil's inductance?
What is the effect of decreasing the number of turns on a coil's inductance?
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Decreases inductance. Fewer turns reduce magnetic flux linkage proportionally.
Decreases inductance. Fewer turns reduce magnetic flux linkage proportionally.
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What does the negative sign in $-\frac{dI}{dt}$ indicate in Faraday's Law?
What does the negative sign in $-\frac{dI}{dt}$ indicate in Faraday's Law?
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Direction opposes change. Indicates EMF opposes the current change (Lenz's law).
Direction opposes change. Indicates EMF opposes the current change (Lenz's law).
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State the energy stored in an inductor formula.
State the energy stored in an inductor formula.
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$E = \frac{1}{2} \times L \times I^2$. Energy proportional to inductance and current squared.
$E = \frac{1}{2} \times L \times I^2$. Energy proportional to inductance and current squared.
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What is the induced emf when L=0.1 H and the current change is 10 A/s?
What is the induced emf when L=0.1 H and the current change is 10 A/s?
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$\text{emf} = -1 \text{ V}$. Using $\text{emf} = -L \frac{dI}{dt} = -0.1 \times 10$.
$\text{emf} = -1 \text{ V}$. Using $\text{emf} = -L \frac{dI}{dt} = -0.1 \times 10$.
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State the proportional relationship between inductance and coil length.
State the proportional relationship between inductance and coil length.
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Inversely proportional. Length in denominator creates inverse relationship.
Inversely proportional. Length in denominator creates inverse relationship.
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What is the inductance of a coil with back emf of 12 V and $\frac{dI}{dt} = 4 A/s$?
What is the inductance of a coil with back emf of 12 V and $\frac{dI}{dt} = 4 A/s$?
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$L = 3 \text{ H}$. From $L = \frac{\text{emf}}{dI/dt} = \frac{12}{4}$.
$L = 3 \text{ H}$. From $L = \frac{\text{emf}}{dI/dt} = \frac{12}{4}$.
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Which type of inductance involves two electrical circuits?
Which type of inductance involves two electrical circuits?
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Mutual inductance. Coupling between separate coils or circuits.
Mutual inductance. Coupling between separate coils or circuits.
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What effect does tightly winding a coil have on its inductance?
What effect does tightly winding a coil have on its inductance?
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Increases inductance. Tighter winding increases turns per unit length.
Increases inductance. Tighter winding increases turns per unit length.
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What is the effect of a core material with higher permeability?
What is the effect of a core material with higher permeability?
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Increases inductance. Higher permeability concentrates magnetic field lines better.
Increases inductance. Higher permeability concentrates magnetic field lines better.
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What is the inductance of a coil if the self-induced emf is 5V and $\frac{dI}{dt} = 2 A/s$?
What is the inductance of a coil if the self-induced emf is 5V and $\frac{dI}{dt} = 2 A/s$?
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$L = 2.5 \text{ H}$. From $\text{emf} = L \frac{dI}{dt}$, so $L = \frac{5}{2}$.
$L = 2.5 \text{ H}$. From $\text{emf} = L \frac{dI}{dt}$, so $L = \frac{5}{2}$.
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Identify the factor that does not affect inductance.
Identify the factor that does not affect inductance.
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Temperature. Inductance depends on physical geometry, not thermal properties.
Temperature. Inductance depends on physical geometry, not thermal properties.
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