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Time constant in an R-L circuit is defined as the time taken by the current to become
  • a)
    36.8% of the final value
  • b)
    36.8% of the initial value
  • c)
    63.2% of the final value
  • d)
    None of these
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
Time constant in an R-L circuit is defined as the time taken by the cu...
Time Constant in an R-L circuit refers to the time taken by the current to reach approximately 63.2% of its final value after a change in voltage or current is applied to the circuit.

The time constant is determined by the values of resistance (R) and inductance (L) in the circuit. It is denoted by the symbol τ (tau) and is calculated using the formula:

τ = L / R

where:
τ = time constant
L = inductance in henries (H)
R = resistance in ohms (Ω)

Explanation:
To understand why the time constant represents 63.2% of the final value, we need to consider the behavior of an R-L circuit when a voltage or current is applied.

- Initially, when a change in voltage or current is applied, the current in an inductor (L) cannot change instantaneously. It builds up gradually.
- As time progresses, the current increases, but it takes a certain amount of time for the current to reach its maximum value.
- The time constant represents the time it takes for the current to reach 63.2% of its final value.
- After one time constant (τ), the current in the circuit is approximately 63.2% of the final value.
- It takes multiple time constants for the current to reach its final value. However, the majority of the change occurs within the first few time constants.

In other words, the time constant is a measure of the rate at which the current in an R-L circuit approaches its final value. It indicates how quickly the current rises when a voltage or current is applied and how long it takes for the current to settle at its final value.

Hence, the correct answer is option C: 63.2% of the final value.
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Community Answer
Time constant in an R-L circuit is defined as the time taken by the cu...
An L-R Series Circuit consists basically of an inductor of inductance L, connected in series with a resistor of resistance R. The resistance “R” is the resistive value of the wire turns or loops that go into making up the inductors coil.
Time constant (τ) –
The time constant is defined as the time required for the circuit to reach 63.2% of the final value (steady-state value).
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