Phet Electric Field Hockey Level 3 Solution

Getting Past the Charge Placement Puzzle

Level 3 in Phet Electric Field Hockey throws in a second charge to guard the goal, which immediately screws over the simple one-charge strategies that work fine at levels one and two. The puck needs to curve around that barrier charge without hitting it, and if you place charges blindly you spend twenty minutes watching the puck deflect into the obstacle every single time. The actual solution comes down to thinking about field lines rather than brute-force trial and error. You're working with a negative pylon charge inside the goal and a positive barrier charge somewhere near the scoring zone. What matters is creating a field path that guides the puck from the starting line toward the goal while keeping it clear of that barrier. Positive test charges move with the field, negative ones fight against it, so your goal charges need to push or pull the puck along a curved trajectory that arcs around the obstruction.

Phet Electric Field Hockey Level 3 Solution

Here is what I found actually works after going through probably fifty attempts across different configurations. Place a positive charge roughly opposite the barrier charge, on the far side of the rink from where the puck starts. This creates a repulsive field that pushes the puck away from the barrier early in its path. Then position a second positive charge closer to the goal but offset laterally, not directly in line with the puck's start point. This one bends the trajectory inward toward the goal mouth without sending the puck straight into the barrier. The tricky part is getting the strengths right. In the simulation each charge can be set to positive or negative with varying magnitudes, but more is not better. A charge that is too strong will overcurve the puck and send it careening out of bounds or directly at the barrier anyway. I usually set the first charge to around three times the base unit and the second to about two times. If the puck still hits the barrier, move the second charge slightly farther from the goal axis and reduce its strength. If the puck doesn't curve enough to reach the goal, increase the first charge's magnitude incrementally by one unit and retry. I ran into a specific edge case once where the barrier charge was positioned unusually close to the goal line, leaving almost no lateral space for the puck to thread through. The standard two-charge setup wouldn't produce a tight enough turn without the puck clipping the barrier. What worked was adding a third positive charge placed behind the puck's starting position rather than in front of it. This created an initial push that accelerated the puck before the curve began, giving the later charges more momentum to work with and allowing a sharper turn in the remaining space. It took me about ten tries to figure out that positioning the third charge diagonally behind and to the side of the start point produced the cleanest launch angle.

Another thing most people miss is that the puck's mass doesn't change between levels. The simulation keeps it constant, which means the field forces need to do all the steering work. Beginners often try to compensate by placing charges too close to the puck's starting position, expecting a stronger initial force to carry it through. But charges that are too close create an excessively steep gradient that launches the puck in a nearly straight line before the field has a chance to curve it. You want charges far enough away that the field is gradual, giving the puck time to respond to the lateral forces. The simulation itself has some limitations worth noting. The field visualization updates in discrete steps rather than continuously, so small adjustments to charge placement can produce surprisingly nonlinear changes in the puck's trajectory. A movement of one grid unit on your part can shift the puck's path by several grid units at the goal. There is no fine-tune mode or slow-motion playback, so once you hit start you are committed to watching the full run. This means your mental model of the field needs to be reasonably accurate before you begin, because debugging mid-animation is impossible. If you keep failing with positive charges, try swapping one to negative. A negative charge placed between the puck's expected path and the barrier can actually help by attracting the puck toward the center of the rink, creating a wider arc that naturally avoids the obstacle. It feels counterintuitive at first because you would expect a negative charge to pull the positively charged puck into the barrier, but when positioned correctly it acts as a deflector rather than a trap.

The download for the Phet simulation is available directly from the University of Colorado Boulder's website atphet.colorado.edu. You do not need a special version for level three; the standard interactive simulation includes all levels. If the browser version is acting sluggish on your machine, downloading the standalone applet version usually improves responsiveness significantly, particularly when you are running multiple charge placements and need to watch the field lines update in real time. Quick reference for the core configuration: One positive charge, magnitude three, placed far from the barrier on the opposite side of the rink. Second positive charge, magnitude two, offset laterally near the goal. Optional third positive charge, magnitude one, positioned diagonally behind the puck's start if the barrier is very close to the goal line. Adjust each charge in increments of one unit and note the resulting trajectory before making the next change.

This approach usually gets the puck into the goal within three or four attempts if your initial placement is roughly in the right quadrant. The main bottleneck is finding the exact lateral offset for the second charge, which depends on the barrier's specific position in that particular level iteration. Once you dial it in, the simulation runs clean and the puck scores without any contact with the obstacle charge.