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AQA · GCSE · Physics · Higher

Current from Charge Flow

Q10.3 4 marks

The fuse wire melts when there is a charge flow of 2.0 C for 400 ms.

charge flow = current × time, Q=ItQ=It

Calculate the current in the fuse wire.

Use the Physics Equations Sheet.

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Marking points

  1. 1 Converts 400 ms to 0.400 s.
  2. 2 Uses Q = It with 2.0 C.
  3. 3 Rearranges correctly for current.
  4. 4 Obtains 5.0 A, subject to official error-carried-forward guidance.

Full-mark answer

400 ms=0.400 s400\text{ ms}=0.400\text{ s}. Using Q=ItQ=It, I=Q/t=2.0/0.400=5.0 AI=Q/t=2.0/0.400=5.0\text{ A}.

Why this answer loses marks

I used the time in milliseconds directly in Q = It.

Convert the time to seconds before rearranging charge flow = current × time for current.

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