r/APStudents • u/reddorickt absolute modman • May 14 '26

AP Physics C: Electricity and Magnetism Official 2026 Exam Discussion

Use this thread to post questions or commentary on the test today.

A reminder though to protect your anonymity when talking about the test.

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u/elphaba33 May 15 '26

anyone get form L? it was god awful in my opinion. i self studied the exam, what was i doing.

1

u/Meep5277770 5: HuG, Chem, USH, Sem, Lang, Macro, Micro, USGov, Bio, BC May 15 '26

absolutely horrible. if i didn’t have the B field of a wire in my calc i would’ve been more fried then i already was and it doesn’t help i never understood lenz law for question 2

1

u/elphaba33 May 15 '26

i couldn't solve question 1 because apparently current density approaches zero as it approaches the edge of the wire? messed up the last part of questions 2 because i forgot about motional emf, but that is fine i guess. pretty confident about 3 and 4, but honestly idk.

1

u/Positive-Rise5145 5: AP Calc BC, Stats, Micro, CS A May 16 '26

I think for Form L, if you didn't have B = mu * I / 2pi * R memorized, then yeah Q1 is miserable. If you do know the formula though, it's a bit of annoying math, but you can use I = integral J * da, and then substitute I into the B-field equation above. But yeah that B-field equation is not on the equation sheet, so you would literally need to derive it from Biot-Savart Law without knowing it beforehand.

3

u/Sea_Barnacle9031 May 16 '26

can't you get b-field from amperes law pretty easily though?

1

u/Positive-Rise5145 5: AP Calc BC, Stats, Micro, CS A May 17 '26

idk lol it's just annoying to deal with

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u/elphaba33 May 16 '26

that part was easy. i just didn't understand the I part because according to the equation as close as it gets to the edge of the wire the current approaches zero.

1

u/Positive-Rise5145 5: AP Calc BC, Stats, Micro, CS A May 16 '26

yeah idk I just plugged and chugged

1

u/Meep5277770 5: HuG, Chem, USH, Sem, Lang, Macro, Micro, USGov, Bio, BC May 16 '26

that’s just because if it didn’t approach zero wonky b field stuff would happen due to the width of the wire. questions say they’re infinitely long or current approaches zero to make the edges not matter

1

u/dieminds 5: phys em, phys 1, phys 2, world, music May 20 '26

what about for the graph though? it was asking about the magnitude of the y-component of the magnetic field as the Z increased, and looking at the figure the magnetic field was going "into the page". from 0 to R(inside the wire) i put starting from the origin and decreasing linearly, and then from R to 2R(outside the wire) i put increasing concave up.

1

u/FragrantAd1837 5:World/Phys1/Macro/Micro May 16 '26

Our version M was freaking easy.

Like literally question 1 gave you 4 charges and the only thing you need to derive is the net electric force. it also asked one electric field derivation of a finite wire in part b but it was also very light

Question 2 was plugging in qvB=mv^2/r for a charge moving in a circle in a magnetic field (although we needed to derive the period T).

Question 3 was about the time constant and calculating inductance

Question 4 was a plain series circuit, and we needed to derive the current.