JEE Advanced

	Paper	Asks	Answer
problem_1/	2022, Paper 1, question 10	which of four claimed currents are correct	all four of (A), (B), (C), (D)
problem_2/	2015, Paper 2, question 8	the current I through R (= 2 Ω)	I = 1 A

Neither is a board. They are here because the question a physics paper asks once is the question a board asks all day (is this claim about my circuit true?), and the kernel answers it the same way either time: the potentials are a value, Kirchhoff’s current law is a constraint, and the paper’s claim is a constraint the checker decides rather than a comment nobody re-reads.

The pair is worth two folders because they show different halves of that. problem_1 checks four claims at once, exactly the four the paper offers. problem_2 checks one, and then checks two more the paper never asks for: that two of its ten resistors carry no current at all, which is the whole trick of the question and the reason its answer is a round ampere.

Both work the same way, and neither solves anything:

• the program claims the node potentials, derives every branch current from them by Ohm’s law, and writes Kirchhoff’s current law once per node;
• solve.py beside it lowers the same graph to SPICE through fang.simulation and runs ngspice, which is where the potentials came from;
• out/rationale.md carries the question, every resistor’s value and current, and the answer, because each of those is an entity in the graph.

The two paths are independent: ngspice solves, the kernel decides.

Running them

fang check examples/jee_advanced/problem_1/problem_1.py
fang check examples/jee_advanced/problem_2/problem_2.py

python examples/jee_advanced/problem_1/solve.py   # needs ngspice on PATH
python examples/jee_advanced/problem_2/solve.py

In this folder

• problem_1: JEE (Advanced) 2022, Paper 1, question 10, written as a fang program: the diamond of eight 1 Ω resistors and two batteries below, with each of its four claimed currents a constraint the kernel decides.
• problem_2: JEE (Advanced) 2015, Paper 2, question 8, written as a fang program: the ten resistors and one 6.5 V battery below, with the one current the paper asks for, I through R, claimed and checked. I = 1 A.