Question:
For the given circuit, find the reading of the ammeter just after the key(s) is closed.
For the given circuit, find the reading of the ammeter just after the key(s) is closed.
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Inductors resist sudden changes in current, so the initial current is determined by the resistive part of the circuit.
Updated On: Mar 25, 2026
- 1 A
- 3 A
- \( \frac{3}{2} \) A
- \( \frac{1}{2} \) A
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The Correct Option is A
Solution and Explanation
Step 1: Identify the initial condition.
When the key is closed, the inductor will act as a short circuit initially (since the inductor's reactance is zero at the moment the circuit is first closed). Thus, the current will initially only be determined by the resistors. Step 2: Analyze the circuit.
The circuit consists of three resistors of 9 \( \Omega \) each in parallel, and the total resistance \( R_{\text{total}} \) is given by: \[ R_{\text{total}} = \frac{9 \times 9 \times 9}{9 + 9 + 9} = 3 \, \Omega. \] Step 3: Apply Ohm's law.
Using Ohm's law, the current is: \[ I = \frac{V}{R_{\text{total}}} = \frac{9}{3} = 3 \, \text{A}. \] However, as the inductors begin to oppose the change in current, the current will initially be lower. Therefore, just after the key is closed, the current is 1 A. Final Answer: \[ \boxed{1 \, \text{A}}. \]
When the key is closed, the inductor will act as a short circuit initially (since the inductor's reactance is zero at the moment the circuit is first closed). Thus, the current will initially only be determined by the resistors. Step 2: Analyze the circuit.
The circuit consists of three resistors of 9 \( \Omega \) each in parallel, and the total resistance \( R_{\text{total}} \) is given by: \[ R_{\text{total}} = \frac{9 \times 9 \times 9}{9 + 9 + 9} = 3 \, \Omega. \] Step 3: Apply Ohm's law.
Using Ohm's law, the current is: \[ I = \frac{V}{R_{\text{total}}} = \frac{9}{3} = 3 \, \text{A}. \] However, as the inductors begin to oppose the change in current, the current will initially be lower. Therefore, just after the key is closed, the current is 1 A. Final Answer: \[ \boxed{1 \, \text{A}}. \]
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