Advanced Qualification · A-001 Advanced theory · A-001-001-001
What is the meaning of the term "time constant" in an RL circuit ?
- A The time required for the voltage in the circuit to build up to 63.2% of the maximum value
- B The time required for the voltage in the circuit to build up to 36.8% of the maximum value
- C The time required for the current in the circuit to build up to 63.2% of the maximum value
- D The time required for the current in the circuit to build up to 36.8% of the maximum value
Correct answer: C — The time required for the current in the circuit to build up to 63.2% of the maximum value. From the official ISED question bank, verified word for word.
Why
In an RL circuit, which contains a resistor and an inductor, the current does not jump instantly to its full strength when power is applied. The full explanation — and one for every question — is in Pro.
Practise this section
Advanced theory: time constants, reactance, impedance, resonance, Q, and the mathematics behind tuned circuits.