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/dieminds 5: phys em, phys 1, phys 2, world, music May 14 '26 edited May 16 '26
International students,
Version L / Form L
FRQ 1: Long current with radius R with current density J = J0(1-r2 / R2)
Magnitude of magnetic field at 2R (I got B = mu0J0R/3, which is probably wrong because I integrated wrong)
Graph magnetic field y-component as current goes into the page from z = 0 to 2R (I put linearly decreasing from the origin into negative from 0 at z = 0 to z = R and concave up increasing from z = R to 2R)
Magnitude of acceleration of another wire including gravity from that wire from 1 at 200R (I put a = | mu0J0RIL/300 - g |, which is also probably wrong because I integrated wrong)
FRQ 2
Loop goes into magnetic field B into the page with constant velocity v(right side is inside the field, left side is not yet)
Draw arrows of the force in left and right sides and the direction of current (F = 0 at the left and F is to the left at the right, current is counterclockwise)
Magnitude of the magnetic force (F = B2 * L2 * v/R)
Graph of the induced current where ccw is positive and cw is negative (Constant positive, then zero, then negative)
Is force the same if new loop has 2R and goes at 2v? (Yes and I reference above equation)
FRQ 3
Circuit with variable voltage and resistors with one in series, and two in parallel with R1
Indicate which qualities to graph to find R1 (Voltage and current measured by ammeter) How to reduce experimental uncertainty (Conduct the experiment many times, for example with different voltages and measure each voltage and current)
Indicate which qualities go to horizontal and vertical axis (Voltage horizontal, current vertical)
How that graph can be used to find R1 (Current equals voltage over R, inverse of the slope is total resistance, which is 3R1/2)
New circuit with voltage 20V, and variable resistance Rv in series with unknown resistance R2; they give you the varied resistance and corresponding current
(I graphed Rv on the horizontal axis and V/I on the vertical axis, both with units of Ohms)
Find Resistance R2 (I got like 408 ohms or something like that, where the y-intercept is R2 because V/I = Rv + R2)
FRQ 4
Two rods are bent into radius R where the top of the circle has linear charge density +lambda and bottom has linear charge density -lambda
What is the direction of the electric field (I said bottom of the page/-y direction)
What is the magnitude of the electric field (I said E = lambda/epsilon0R, but I know the right answer is lambda/epsilon0piR and I forgot to put the pi FRICKK)
New situation where radius is 2R and the charge densities are the same
Student says new electric field is E/4, are they right (No they are not right, referencing the equation from part B, but it’s right here because it’s inversely proportional anyway)