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  1. AP Physics C E M
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What is the effect of increasing the inductance (L) in an LR circuit?

It increases the time constant (τ\tauτ), causing the current to change more slowly.

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What is the effect of increasing the inductance (L) in an LR circuit?

It increases the time constant (τ\tauτ), causing the current to change more slowly.

What happens when a switch is closed in an LR circuit?

The current starts to increase, and the inductor generates a back emf that opposes the change in current.

What is the effect of energy dissipation in resistors in an LR circuit?

It leads to a decrease in the inductor's stored energy over time, as the energy is converted to heat.

What happens to an LR circuit after a very long time?

The inductor acts like a short circuit, and the current reaches its maximum value, determined by the battery's emf and the resistance.

What is the effect of increasing the resistance (R) in an LR circuit?

It decreases the time constant (τ\tauτ), causing the current to reach its steady-state value more quickly and reduces the maximum current.

What happens when the current changes in an LR circuit?

The inductor induces an emf that opposes the change in current, according to Lenz's Law.

How do you apply Kirchhoff's loop rule to an LR circuit?

  1. Identify a closed loop in the circuit. 2. Sum the voltage drops across each element in the loop, considering the sign. 3. Set the sum equal to zero: E−IR−LdIdt=0\mathcal{E} - IR - L \frac{dI}{dt} = 0E−IR−LdtdI​=0.

What is the process for calculating the time constant (τ\tauτ) in an LR circuit?

  1. Identify the inductance (L) and the equivalent resistance (ReqR_{eq}Req​) in the circuit. 2. Use the formula: τ=LReq\tau = \frac{L}{R_{eq}}τ=Req​L​.

Describe the steps to analyze the transient state of an LR circuit.

  1. Apply Kirchhoff's loop rule to obtain a differential equation. 2. Solve the differential equation for the current as a function of time, I(t). 3. Analyze how the current, voltage, and energy change over time using exponential functions.

How do you determine the steady-state behavior of an inductor?

  1. After a long time, treat the inductor as a short circuit (a wire with zero resistance). 2. Calculate the current through the circuit using Ohm's law, considering only the battery's emf and the total resistance.

What are the steps to determine the current in an LR circuit immediately after closing a switch?

  1. Recognize that the current through the inductor cannot change instantaneously. 2. If the initial current is zero, the current remains zero immediately after closing the switch.

Label the components in a simple LR circuit diagram.

1: Battery (E\mathcal{E}E), 2: Resistor (R), 3: Inductor (L), 4: Switch