6 An electron is initially at rest A uniform magnetic field

6. An electron is initially at rest. A uniform magnetic field pointing in the positive y-direction is applied to the electron. What happens? a. The electron moves in the ty direction. b· The electron moves in the-y direction. c The electron moves in the-x direction. d. The electron moves in the-z direction. e. The electron does not move. 7. Consider an ideal circuit Consider an ideal circuit connected to a battery and a resistor. If a second identical resistor is connected in series to the first resistor, which of the following is true? a. The current will be cut in haltf. b. The current will double. c. The current will not be affected. 8. At the turn of the 20th Century, the hydrogen atom was modeled as an electron moving in a uniform circular orbit about a stationary proton, somewhat analogous to how a planet moves under the influence of the Sun\'s gravity. What should be one observational consequence of such a model? Note: the movement of the electron in its orbit establishes an effective electric current All hydrogen atoms should be negatively charged. The electron\'s orbit should be unaffected by an exterior magnetic field. The proton should feel a magnetic force due to the electron. The electron should feel a magnetic force due to the proton. The electron will generate a magnetic field. a. b· d. e. 9. Suppose a metal loop stands vertically on a table. The loop begins to spin such Which of the following uniform that its axis of rotation points straight upward. magnetie fields will NOT induce a current in the loop? a. A magnetic field directed due North. b. A magnetic field directed due South. c. A magnetic ficld directed straight upward. d. A magnetic field directed due Northwest. e. Any magnetic field will induce a current in the loop. 10. A vertical wire carries current 1 directed in the negative y-direction (down the page). A uniform magnetic field directed into the page is applied around the wire. What happens? a. The wire bends to the left. b. The wire bends to the right · The wire shrinks.

Solution

6) Force on electron = e(v X B)

Since, v = 0, F = 0.

Answer is e. The electron does not move.

7) I=V/R

When the new resistor is added, the resistance is now 2R. Hence, current,

I₁=V/2R=I/2

Answer is a.) The current will be cut in half.

8) The elecron moving in an orbit will generate an internal magnetic field as explained by hydrogen fine structure and Zeeman effect. So the answer is e.

9) A magnetic field directed straight upward since the magnetic flux, required to generate current, does not pass through the loop. Answer is c.

10) The magnetic force is given by IL X B. Hence, the wire will experience a force in the +x direction. The answer is b.