(Multiple choice)

(1)

When a cathode-ray tube is placed horizontally in a magnetic field that is directed vertically upward, the electrons emitted from the cathode follow one of the dashed paths to the face of the tube in Figure. The correct path is __________.?

(a) 1?

(d) 4?

(b) 2?

(e) 5?

(c) 3

(2) True or false:?

The magnetic force does not accelerate a particle because the force is perpendicular to the velocity of the particle.

(3)?True or false:?

(a) The magnetic force on a moving charged particle is always perpendicular to the velocity of the particle.?

(b) The torque on a magnet tends to align the magnetic moment in the direction of the magnetic field.?

(c) A current loop in a uniform magnetic field behaves like a small magnet.?

(d) The period of a particle moving in a circle in a magnetic field is proportional to the radius of the circle.?

(e) The drift velocity of electrons in a wire can be determined from the Hall Effect.

(4)

A proton with a charge +e is moving with a speed v at 50? to the direction of a magnetic field.?

The component of the resulting force on the proton in the direction of is?

(a) evB sin 50? cos 50?.?

(b) evB cos 50?.?

(c) Zero.?

(d) evB sin 50?.?

(e) None of these.

(5)

A positively charged particle is moving northward in a magnetic field. The magnetic force on the particle is toward the northeast. W hat is the direction of the magnetic field??

(a) Up?

(b) West?

(c) South?

(d) Down?

(e) This situation cannot exist.

(6)

A ⁷Li nucleus with a charge of +3e and a mass of 7 u (1 u = 1.66 ? 10^?27 kg) and a proton with charge +e and mass 1 u are both moving in a plane perpendicular to a magnetic field The two particles have the same momentum. The ratio of the radius of curvature of the path of the proton R_p to that of the ⁷Li nucleus, R_Li is?

(a) R_p/R_Li = 3.?

(b) R_p/R_Li = 1/3.?

(c) R_p/R_Li = 1/7.?

(d) R_p/R_Li = 3/7.?

(e) No ?ne of these.

(7)

An electron moving with velocity v to the right enters a region of uniform magnetic field that points out of the paper. After the electron enters this region, it will be?

(a) Deflected out of the plane of the paper.?

(b) Deflected into the plane of the paper.?

(c) Deflected upward.?

(d) Deflected downward.?

(e) Un deviated in its motion.

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ICIE 5 В