Physics

Problem

Current in a wire is

2.0\,\text{A}

for the first

3.0\,\text{s}

and then

0.50\,\text{A}

for the next

2.0\,\text{s}

. What total charge passes a cross-section of the wire during the entire

5.0\,\text{s}

interval? a)

6.25\,\text{C}

7.0\,\text{C}

6.0\,\text{C}

5.0\,\text{C}

Intuitive explanation

Charge is the total "amount of flow" through a wire, and current tells you the rate of that flow. Since the current changes partway through, you can't just multiply $I \times t$ once—instead, break the time into intervals where current is constant, calculate the charge for each piece using $Q = It$ , then add them together.

Intuitive explanation

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