Chapter 332 - 182: Tracing the Lines

Chapter 332: Chapter 182: Tracing the Lines

The sound of the outdoor AC unit filtered in through the windowpane.

HUMMMMM.

The AC in the room was cranked up high. The slats on the vent oscillated up and down, sending streams of cool air toward the desk.

Zhang Qiang was sitting in a chair.

He clutched a pencil. The eraser on its end was chewed into a pitted mess, and even the metal band holding it was dented.

A workbook titled Ninth Grade Physics: Summer Bridge & Enrichment lay open on the desk.

The pages were thin.

On one of the middle pages, a particular problem had been erased so many times that the paper had started to fray. Grayish-black pencil smudges smeared the page, making a mess.

Zhang Qiang stared at the problem.

His eyes followed the solid black line on the diagram.

The line reached a junction and split in two. One branch went up, connecting to a circle with a cross inside; the other went down, connecting to a circle with an ’A’ inside.

The pencil in Zhang Qiang’s hand rested on the ’A’.

Its tip tapped the junction, then tapped again.

He ran a hand through his hair in frustration.

He tossed the pencil onto the desk.

The pencil rolled twice before hitting the base of the desk lamp and coming to a stop.

"What the hell is this supposed to be?"

Zhang Qiang leaned back, and the chair let out a CREAK.

He turned to look beside him.

Chen Zhuo was sitting in the swivel chair Zhang Qiang usually used for gaming.

He was leaning back, legs casually crossed.

In his hand was a carton of milk that Zhang Qiang had just gotten from the fridge.

Chen Zhuo chewed on the straw and swallowed a mouthful of milk.

He didn’t say anything, just watched Zhang Qiang.

"Brother Zhuo, look at this."

Zhang Qiang pointed at the workbook on his desk, his voice verging on madness.

"Is this book even written in English?"

Chen Zhuo kept the straw in his mouth.

He tilted his chin up slightly, signaling for him to go on.

"The book says the electric current flows from the positive terminal to the negative terminal. Fine, I get that."

Zhang Qiang picked up his pencil, gesturing at the diagram.

"But look at this problem! The wires are a tangled mess, and there are three switches! S1 is closed, S2 is open, S3 is closed."

Zhang Qiang jabbed the tip of his pencil at the symbol for a lightbulb—the circle with a cross in it.

"One moment it’s closed, the next it’s open, the whole circuit is a disaster. When the current gets to this junction, does it go left or right?"

Chen Zhuo let go of the straw.

"What does the book say?"

"The book says the current will take the path with the greater potential difference, and at a split, it will divide proportionally based on resistance."

Zhang Qiang rolled his eyes.

"What the hell is ’potential difference’? What does ’proportionally’ even mean? These wires all look identical! How am I supposed to know which path is ’bigger’ or ’smaller’?"

Zhang Qiang pointed to another solid line nearby that wasn’t connected to anything.

"And this thing! The book says this is a wire, with zero resistance. The current goes through here, so it just skips the lightbulb."

Zhang Qiang’s face was a mask of disbelief.

"Why?! Doesn’t electricity just go everywhere? The lightbulb is right there! It won’t even pop in for a quick look?!"

Chen Zhuo looked at Zhang Qiang’s indignant expression.

A faint smile touched the corners of his lips.

He didn’t sit up, remaining leaned back in the chair.

His gaze fell on Zhang Qiang’s pen holder, which was crammed with all sorts of stationery.

Chen Zhuo reached out.

He pulled a red marker out of the pen holder.

Then a blue one.

These were the highlighters Zhang Qiang normally used to mark key passages in his literature textbook.

Chen Zhuo tossed the two markers to Zhang Qiang.

The two markers landed on Zhang Qiang’s physics workbook, right on top of the frayed circuit diagram.

Zhang Qiang paused, looking from the markers to Chen Zhuo.

"What for?"

Chen Zhuo placed his milk carton on the edge of the desk.

"Put down the pencil."

Zhang Qiang glanced at Chen Zhuo’s expression and obediently pushed his pencil aside.

"Uncap them," Chen Zhuo said.

Zhang Qiang reached out, uncapped the red and blue markers, and held them in his hands.

"Look at the problem."

Chen Zhuo pointed to the symbol for the battery on the page.

A long vertical line and a short one.

"The long line is the positive terminal, the short one is the negative. Don’t worry about which way the current flows, and forget about ’potential difference’."

Chen Zhuo’s voice was even.

"Grab the red marker."

Zhang Qiang raised his right hand.

"Touch the tip of the marker to the long line of the battery symbol."

Zhang Qiang did as he was told.

The red tip touched the paper, blooming a small dot of ink.

"Trace along the solid line."

Chen Zhuo watched him.

"When you reach a split, trace both paths. Color every connected wire red."

Following the instructions, Zhang Qiang traced the wires on the diagram with the red marker.

The red ink covered the original black lines.

"Stop."

The tip of the marker stopped just before a circle with a cross in it—a lightbulb.

"When you hit a component—a lightbulb, a resistor—you stop. You can’t go through it," Chen Zhuo said.

Zhang Qiang nodded, stopping the red marker in front of the lightbulb.

"Go back and color all the other paths you can take. Stop at open switches, too."

Zhang Qiang’s wrist moved.

Less than ten seconds later...

Half of the diagram’s black lines were now a conspicuous red. The color spread all the way to the front of lightbulb L1, the front of resistor R1, and just past the closed switch S1.

"Switch to the blue marker," Chen Zhuo said.

Zhang Qiang put down the red marker and picked up the blue one.

"Touch it to the battery’s short line—the negative terminal."

The blue tip touched the paper.

"Same method."

Chen Zhuo leaned back further into his chair.

"Trace the lines. Stop at a lightbulb, stop at a resistor, stop at an open switch."

Blue ink began to spread across the page.

It mirrored the red lines from before.

The blue line passed through the ammeter, went around the bottom of the sliding rheostat, and finally stopped at the other side of lightbulb L1 and resistor R1.