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ConcepTest 28.5 Velocity Selector

E. B = ?. v. electrons. ConcepTest 28.5 Velocity Selector. What direction would a B field have to point for a beam of electrons moving to the right to go undeflected through a region where there is a uniform electric field pointing vertically upward?. 1) up (parallel to E )

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ConcepTest 28.5 Velocity Selector

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  1. E B = ? v electrons ConcepTest 28.5 Velocity Selector What direction would a B field have to point for a beam of electrons moving to the right to go undeflected through a region where there is a uniform electric field pointing vertically upward? 1) up (parallel to E ) 2) down (antiparallel to E ) 3) into the page 4) out of the page 5) impossible to accomplish

  2. E B = ? v electrons ConcepTest 28.5 Velocity Selector What direction would a B field have to point for a beam of electrons moving to the right to go undeflected through a region where there is a uniform electric field pointing vertically upward? 1) up (parallel to E ) 2) down (antiparallel to E ) 3) into the page 4) out of the page 5) impossible to accomplish Without a B field, the electrons feel an electric force downwards. In order to compensate, the magnetic force has to point upwards. Using the right-hand rule and the fact that the electrons are negatively charged leads to a B field pointing out of the page.

  3. I B ConcepTest 28.6b Magnetic Force on a Wire II 1) left 2) right 3) zero 4) into the page 5) out of the page • A horizontal wire carries a current and is in a vertical magnetic field. What is the direction of the force on the wire?

  4. I B ConcepTest 28.6b Magnetic Force on a Wire II 1) left 2) right 3) zero 4) into the page 5) out of the page • A horizontal wire carries a current and is in a vertical magnetic field. What is the direction of the force on the wire? When the current is parallel to the magnetic field lines, the force on the wire is zero.

  5. z B y x ConcepTest 28.7a Magnetic Force on a Loop I 1) + x 2) + y 3) zero 4) - x 5) - y • A rectangular current loop is in a uniform magnetic field. What is the direction of the net force on the loop?

  6. z B y x ConcepTest 28.7a Magnetic Force on a Loop I 1) + x 2) + y 3) zero 4) - x 5) - y • A rectangular current loop is in a uniform magnetic field. What is the direction of the net force on the loop? Using the right-hand rule, we find that each of the four wire segments will experience a force outwards from the center of the loop. Thus, the forces of the opposing segments cancel, so the net force is zero.

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