Question 1

A particle with charge $$q = -1\ \mathrm{C} is $$moving in the positive $$z-$$direction at $$5\ \mathrm{m/s}. $$The magnetic field at its position is $$\vec{B} = 3\hat{x} + 4\hat{y}\ \mathrm{T}. $$What is the magnetic force on the particle?

Accepted Answer

$$(-20\hat{x} - 15\hat{y})\ \mathrm{N}$$

Question 2

A positively charged particle enters chamber 1 (see $$image_1) $$and follows the dashed path shown. What is the direction of the magnetic field in chamber 1?

Accepted Answer

Into the page

Question 3

A positively charged particle moves from chamber 1 to chamber 2, following a curved path (see $$image_1). If $$the radius of curvature in chamber 1 is smaller than in chamber 2, what can you conclude about the magnitudes of the magnetic fields $$|B_1$|$$ and $$|B_2$|$$?

Accepted Answer

$$|B_1$| \u003e |B_2$|$$

Question 4

Hans Oersted discovered that a compass needle is deflected when placed near a current-carrying wire. What does this experiment demonstrate?

Accepted Answer

Electric current produces a magnetic field

Question 5

A straight wire of length $$L$$ carries a current $$I$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the magnitude of the force on the wire?

Accepted Answer

$$F = ILB$$

Question 6

A wire of length $$0.5\ \mathrm{m}$$ carries a current of $$2\ \mathrm{A} in a $$region with a uniform magnetic field of $$0.3\ \mathrm{T}$$ perpendicular to the wire. What is the magnitude of the force on the wire?

Accepted Answer

$$0.3\ \mathrm{N}$$

Question 7

Which of the following best describes the direction of the magnetic force on a current-carrying conductor in a magnetic field?

Accepted Answer

Always perpendicular to both the current and the magnetic field

Question 8

A rectangular current loop of area $$A is $$placed in a uniform magnetic field $$\vec{B}$$ such that the field is parallel to the plane of the loop. What is the net force and net torque on the loop?

Accepted Answer

Net force is zero, net torque is $$IAB$$

Question 9

A wire is bent into a semicircle of radius $$R$$ and connected to two straight sections of length $$L$$ each, all in a uniform magnetic field $$\vec{B}$$ perpendicular to the plane. What is the total magnetic force on the wire?

Accepted Answer

$$F = I B (2R)$$

Question 10

The Hall effect is observed when a current-carrying conductor is placed in a magnetic field. What is the physical origin of the Hall voltage?

Accepted Answer

Separation of charges due to the magnetic force

Question 11

A mass spectrometer separates ions based on their mass-to-charge ratio. If the velocity of the ions is doubled, what happens to the radius of their path in the magnetic field?

Accepted Answer

It doubles

Question 12

A current $$I$$ flows through a wire of length $$L in a $$uniform magnetic field $$\vec{B} at an $$angle $$\phi to $$the field. What is the magnitude of the force on the wire?

Accepted Answer

$$F = ILB \sin \phi$$

Question 13

A rectangular loop of wire with width $$w$$ and length $$l$$ carries a current $$I$$ and is placed in a uniform magnetic field $$B as $$shown in $$image_9. $$What is the expression for the torque on the loop?

Accepted Answer

$$	au = I w l B$$

Question 14

Which of the following statements about the force on a closed current loop in a uniform magnetic field is correct?

Accepted Answer

The net force is always zero

Question 15

A wire of length $$0.8\ \mathrm{m}$$ carries a current of $$3\ \mathrm{A}$$ and is placed at an angle of $$30^\circ to a $$uniform magnetic field of $$0.5\ \mathrm{T}. $$What is the magnitude of the force on the wire?

Accepted Answer

$$0.6\ \mathrm{N}$$

Question 16

A current-carrying wire is placed in a uniform magnetic field. If the direction of the current is reversed, what happens to the direction of the magnetic force?

Accepted Answer

It reverses

Week 6 Lec. 2

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