Ch. 22 Flashcards
(6 cards)
Two charged particles move at right angles to a magnetic field and deflect in opposite directions. Can one conclude that the particles have opposite charges?
No. The particles may have charge of the same sign but move in opposite directions along the same line. In this way, they would both move perpendicular to the field, but would deflect in opposite directions.
An electron moves with constant velocity through a region of space that is free of magnetic fields. Can one conclude that the electric field is zero in this region? Explain.
Yes, if an electric field exists in this region of space, and no magnetic field is present, the electric field will exert a force on the electron and causes it to accelerate.
An electron moves with constant velocity through a region of space that is free of electric fields. Can one conclude that the magnetic field is zero in this region? Explain.
No. If the electron moves in the same direction as the magnetic field, or opposite to the direction of the field, the magnetic force exerted on it will be zero. As a result, its velocity will remain constant.
Describe how the motion of a charged particle can be used to distinguish between an electric and a magnetic field.
In a uniform electric field, the force on a charged particle is always in the same direction, leading to parabolic trajectories.
In a uniform magnetic field, the force of charged particles is always right angles to the motion, resulting the circular paths (or) helical trajectories.
Perhaps even more important, a charged particle experiences a force due to an electric field whether it is moving (or) at rest in the magnetic field, the particle must be moving to experience a force.
Explain how a charged particle moving in a circle of small radius can take the same amount of time to complete an orbit as an identical particle orbiting in a circle of large radius.
The radius of curvature is proportional to the speed of the particle. It follows that the particle moving in a circle of large radius (and large circumference) has a proportionally larger speed than the particle moving in a circle of small radius (and small circumference). Therefore, the time required for an orbit (t= d/v) is the same for both particles.
A current-carrying wire is placed in a region with a uniform magnetic field. The wire experiences zero magnetic force. Explain.
A current carrying wire is placed in a region with a uniform magnetic field; experiences zero magnetic force only if the wire points in the same (or) opposite direction as the magnetic field.
In such case,
θ= 0° or 180°
Force experienced f = BIL sin0°
= 0
