A LovattPhysics video helping you understand the different ways magnetic flux through a coil can change and how this effects the induced emf. Aimed at IB and A-level Physics students. Designed for Higher level IB topic 11.1.
Great video and explanation! I have a question though. Why if you alter the shape quicker does the E increase, like you said, and not decrease because its in the denominator? Greeting from Greece!
I'm having issues trying to grasp the 3rd method, how does the magnetic field coming from a particular pole (Say North pole) changes sign to negative. I'm believing that as the magnetic field cuts across the areas of the coil it changes, thereby producing current. But when it rotates how does it really change to a negative by just flipping it over 😩
That is great! Can you please explain why the change in area causes an emf? I mean, if we think of a wire, If a charge is moving through a magnetic field it will experience a force and hence contribute to the current. Is the change in area depicting the factor of velocity of the charge? Faster the area changes, faster the charge moves and hence, greater emf. Is that so?
Vishank Patel this is probably way too late - so sorry for the slow reply! But the reason is that you are changing the number of field lines that cut through the coil. So if you make the area bigger, more field lines cut through the coil and so the flux linkage is higher. Emf is rate of change of flux linkage so changing the area changes the flux linkage and therefore induces an emf. The faster you change the area, the higher the emf. Hope that helps! Sorry its so late!
@@lovattphysics6366 So, does that mean that there exists some area, which already contains all possible field lines, such that increasing it will have no effect on emf?
@@sittingcat8650 consider a solenoid now in the centre of it is where u asked happens every single field line goes inside the solenoid in the middle of the solenoid so that's it
Theoretically, if one were to move a bundle of wire, not changing the orientation or area, through a uniform magnetic field, no emf would be induced. Is this correct?
Hi Neeraj kumar. Great question. In this case it’s not the number of turns that is negative, but the whole side of the equation. The reason it is negative is because of Lenz’s Law which says that any induced current will act in the opposite direction to the change that created it. That’s a fancy way of saying that if there is a positive change in one of the factors (N, B, A or theta) then there will be a negative emf produced. Hope that helps!
How current in your house etc remain same i mean light remain glow when the direction of the coil changes then establishes positive peak and then into negative at mili second
Ehtisham Khan good question. It depends on what sort of light. A filament bulb glows because it is hot, and it doesnt have time to cool down between AC peaks so it has a constant glow. An LED light however isn’t hot. It actually flashes 100 times a second - it’s just too fast for our eyes to see so it looks like it is constantly on! Hope that helps!
Alpha Omega yep, because the flux density of the magnet will change in those areas. However the effect wouldn’t be as noticeable, which is why I did it up and down.
@@lovattphysics6366 uh okay I have been thinking about it for so long but wasn't too sure, and all the videos I've watched do not talk about that motion. Thanks so much for the speedy response, appreciate it!
Alpha Omega no problem. Any time the flux density (aka magnetic field strength) inside the coil changes, emf is induced. The bigger the change, the bigger the emf. If you imagine the flux lines around the magnet, you can predict what movement will get the biggest emf. Hope that helps!
You have to have a changing magnetic flux to induce an emf. AC is produced her because you have to change the direction you’re moving the coil - you can’t keep moving it towards the magnet indefinitely because eventually you would reach the magnet and have to stop and go back. Going back would have the opposite effect on the changing flux and therefore the opposite direction of current. So the short answer is no, you can’t use this to produce DC - you have to add a component called a rectifier which converts AC to DC. Hope that helps!
ram lal in this case we are looking at the normal to the plane of the coil being at 0 degrees to the field. Cos0=1 so we don’t need it. If there is an angle though, you would need to use cos theta. Hope that helps!
