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You search one topic, say rotational motion, and get twenty teachers. You watch the first ten minutes of four of them, like bits of each, and two hours later you have not solved a single problem. That is the cost of hopping, and the fix is simpler than finding the perfect teacher.
Why does switching between online teachers slow you down?
Every teacher builds a topic in their own order, with their own notation, sign conventions and shortcuts. When you switch midway, you spend the first part of each new video relearning the setup instead of moving forward. You also collect half-explanations: the start of one derivation and the end of another, which do not always fit together.
The bigger problem is that watching feels like progress. In six experiments with 2,225 people, Michael Kardas and Ed O'Brien found that the more people watched others perform a skill, such as throwing darts or doing the moonwalk, the more they believed they could do it themselves. Their actual ability did not improve from watching alone. Each new teacher gives you that feeling again, so you keep watching.
Does the clearest teacher help you learn the most?
Not necessarily, and this matters when you are choosing. In a 2013 study by Shana Carpenter and colleagues, students watched a short video of an instructor explaining a science concept, either fluently, standing upright and speaking without notes, or haltingly, slumped and reading from notes. The fluent instructor was rated as more effective and made students predict they would remember more. Lecture fluency did not significantly change how much they actually learned.
So "this teacher explains so well" is a weak reason to switch. A better test is what you can do after the lecture, without the video on.
How do you choose one main source per subject?
Give yourself one week to decide, then stop shopping. Run a short trial:
Shortlist two sources that follow your syllabus in order, such as the NCERT chapter sequence your school uses.
Watch the same topic from each, start to finish, at a pace you can keep.
Close the video and try a few questions on that topic straight away.
Keep the source after which you solved more on your own, and that has enough practice questions to carry you through the whole subject.
Then write it down: one main source each for physics, chemistry, maths or biology. A free, structured option counts too; our guide to free official resources such as NPTEL, SWAYAM and DIKSHA lists some.
When should you use a second teacher?
Only for a gap you can name. Here is how that looks in practice.
Say your main course is on rotational motion and you get stuck on the moment of inertia of a rod about its end. Your gap sentence: "I do not see why the parallel axis theorem adds M times d squared." Now you search for that, watch only the part that answers it, and go back to your main course at the point where you left. Note the gap and the fix in the margin of your notes so you can revise it later.
A few limits keep detours short:
One gap, one detour. Do not let the second video autoplay into a full chapter.
If the same teacher fills your gaps again and again, consider whether they should become your main source, and switch once, at a chapter boundary.
If you keep hitting gaps because you do not know where to begin, plan first. Fermi's AI tutor works out what you already know and builds a plan for the session, so you start from your actual gap.
For a concept gap, a single focused lesson often beats a long video. The Fermi Concept Library has a lesson for each concept in physics, chemistry, biology and mathematics, with its place in the map, so you can fix one idea and return to your main course.
What should you do instead of watching another explanation?
Test yourself. A 2013 review of ten learning techniques by John Dunlosky and colleagues rated practice testing and distributed (spaced) practice as high utility, and rereading as low utility. Rewatching a topic from a new teacher is close to rereading: familiar, comfortable and easy to mistake for learning.
After each lecture from your main source, close it and solve questions. Our guides on how to learn from video lectures by pausing, predicting and testing yourself and on why rereading feels like learning go further.
This week, pick your main source for one subject and write your first gap sentence when you get stuck.
