When a coil joined to a cell, the current through the coil grows with a time constant `tau`. After what time, the current will reach 10% of its steady- state value?

Explanation

To solve the problem of determining the time at which the current through a coil reaches 10% of its steady-state value, we can follow these steps:

### Step 1: Understand the steady-state current
Let \( I_0 \) be the steady-state current value. We want to find the time \( t \) when the current \( I \) reaches 10% of \( I_0 \). Therefore, we can express this as:
\[ I = 0.1 I_0 \]

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