[Physics] How a moving car becomes electrically charged
forces
Car has been electrically charged as it travels along the road.how is this possible?
Best Answer
If the tires aren't conductive enough, the asphalt/concrete surface of the
road acts like fur, and the tires act like amber, and charge separation
occurs at the contact point, then the movement of the wheel does work on
the separated charge. Charge repels, leaking through the axle to the car body,
accumulates on the outer shell of the car. Basically, the tires (on the interior
of the wheel well) are inside a Faraday cup, so this charge will always
migrate to the outside.
Then the (newly discharged) tire surface comes back into contact with the
road, and the cycle repeats.
Tires are black because of carbon (conductive) added particles, said to
make the 'charge separation' event mainly not happen.
You are right in thinking that the car's acceleration is what keeps it in place, but it is important to remember that an object moving at a constant speed in a circle is accelerating (despite not speeding up). The reason for this is that acceleration is defined as a "change in velocity," and velocity is a vector quantity (i.e. it has magnitude and direction). Therefore, the car's centripetal acceleration must have a force corresponding to it through Newton's Second Law (that force is the radial component of the normal force). And by requiring the position of the car to behave in certain ways, we can calculate that force exactly.
So yes, the acceleration is "adding" to the normal force. The sloped track must apply a greater force in the radial direction than it would if the car were not moving because in that situation the car would begin moving along the radial direction (sliding down the ramp). Likewise, it is not moving in the vertical direction (sliding down the ramp) so the normal force in that direction must be greater as well (to exactly cancel its weight). Since the normal force is the vector sum of its radial and vertical components, you can determine the increased normal force.
The truth is that by stating the problem this way, we have required certain constraints on the motion of the car from which we can deduce the forces acting on it by using Newton's Second Law.
Best Answer
If the tires aren't conductive enough, the asphalt/concrete surface of the road acts like fur, and the tires act like amber, and charge separation occurs at the contact point, then the movement of the wheel does work on the separated charge. Charge repels, leaking through the axle to the car body, accumulates on the outer shell of the car. Basically, the tires (on the interior of the wheel well) are inside a Faraday cup, so this charge will always migrate to the outside.
Then the (newly discharged) tire surface comes back into contact with the road, and the cycle repeats.
Tires are black because of carbon (conductive) added particles, said to make the 'charge separation' event mainly not happen.