why can’t we use magnetic brakes instead of friction brakes in cars

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Couldn’t we just apply a magnetic force to the spinning wheel to slow it down?

In: Physics

One thing that comes to mind is that friction brakes still work even when the vehicle is completely off. Run out of fuel? Battery died? You can still stop the vehicle.

That being said, many electric and hybrid cars do use magnetic braking to help recharge the battery, but they still have physical brakes as well.

We can and do. That’s how hybrid cars slow down, and they turn the momentum back into usable energy (by charging the battery).

You could…but you can’t slow down as fast as Friction brakes.

As mentioned, hybrid cars do use magentic brakes principle to Regen. But effectiveness of Regen is diminished as speed is reduced. Under 10mph, there’s basically no effect.

The force of magnetic brakes is proportional to the speed of the vehicle. The brakes would be nearly worthless at low speed. You could make an active electromagnetic brake but it would be heavy and expensive and defeat the point of whatever you were trying to do with it.

It’s called regenerative braking, and it’s used in electric and hybrid vehicles. The electric motor can also act as a generator, recharging the battery. This causes eddy currents that can provide a lot of braking resistance. You don’t want to rely on this to stop a car, because it can’t. The slower you go, the weaker the effect, so you still need a clamping force to bring the car to a complete stop.