Quick answer: The Biot–Savart law gives the field of a current element, dB = (μ₀/4π) I dl × r̂/r², and integrating it yields B = μ₀I/2πd for a long wire and μ₀I/2R at a loop's centre. This AP Physics C test on Ampère's law has 8 questions worth 20 marks, to do in 45 minutes: Ampère’s law, long wire and coil. The mark scheme is on a separate page; free printable PDF.
This AP Physics C test on Ampère’s law test works like a real class test. The mark scheme is on a separate page, so revise with the lesson first.
This test lasts 45 minutes and is marked out of 20. Show each step, give answers with units and write explanations in full sentences. Use μ₀ = 4π × 10⁻⁷ T·m/A. Draw a sketch if it helps you apply the right-hand rule.
Level: AP Physics C (Mechanics and E&M, calculus-based) · Curriculum: AP PC:E&M Unit 12
Ampère’s law test: the test questions
Question 1 Ampère’s law (2 marks)
State Ampère’s law and give one condition under which it is useful for finding B.Question 2 Long wire (2 marks)
Calculate the magnetic field 4.0 cm from a long straight wire carrying 6.0 A.Question 3 Coil (3 marks)
A flat coil has 50 turns of radius 0.10 m and carries 2.0 A. Calculate B at its centre and at a point on its axis 0.10 m from the centre.Question 4 Solenoid (3 marks)
A 0.50 m solenoid has 1500 turns and carries 3.0 A. Calculate n and the field inside, and state the field outside far from the ends.Question 5 Inside a thick wire (3 marks)
A wire of radius 1.5 mm carries 6.0 A uniformly. Calculate B at r = 0.50 mm and at r = 3.0 mm.Question 6 Parallel wires (3 marks)
The diagram shows two parallel wires.Question 7 Zero field on the line (2 marks)
Explain, using the Biot–Savart law, why a straight wire produces no field at a point on its own line.Question 8 Toroid (2 marks)
A toroid has 250 turns and carries 0.80 A. Calculate B at 5.0 cm from its axis, inside the core.
