Question 1

Which of the following statements best describes the difference between electric charges and magnetic poles?

Accepted Answer

Electric charges can exist as monopoles, while magnetic poles always exist as pairs.

Question 2

A charged particle with charge $$q$$ and velocity $$\vec{v}$$ enters a region with a uniform magnetic field $$\vec{B}$$ perpendicular to its velocity. What is the radius $$R of $$the circular path it follows?

Accepted Answer

$$R = \frac{mv}{|q|B}$$

Question 3

Which material is most likely to be repelled by a magnetic field?

Accepted Answer

Diamagnetic material, such as copper

Question 4

A current $$I$$ flows through a long, straight wire. What is the magnitude of the magnetic field $$B at a $$distance $$r$$ from the wire?

Accepted Answer

$$B = \frac{\mu_0$ I}{2\pi r}$$

Question 5

Which of the following best explains why the Earth's magnetic field is important for life?

Accepted Answer

It protects the Earth from the solar wind and allows many organisms to migrate.

Question 6

A velocity selector uses perpendicular electric and magnetic fields to select particles of a specific speed. What is the required speed $$v$$ for a particle to pass through undeflected?

Accepted Answer

$$v = \frac{E}{B}$$

Question 7

Which of the following is a correct statement about the direction of the magnetic force on a moving positive charge?

Accepted Answer

It is perpendicular to both the velocity and the magnetic field, given by the right-hand rule.

Question 8

A solenoid has $$N$$ turns, length $$l$$, and carries current $$I. $$What is the magnitude of the magnetic field $$B$$ inside the solenoid?

Accepted Answer

$$B = \mu_0$ \frac{N}{l} I$$

Question 9

In mass spectrometry, why do ions with different mass-to-charge ratios follow different paths in a magnetic field?

Accepted Answer

Because the radius of curvature depends on $$\frac{m}{q}$$, so different ratios result in different radii.

Question 10

Which of the following is a real-world biomedical application of solenoids?

Accepted Answer

Magnetic Resonance Imaging (MRI)

Question 11

A current-carrying wire is placed parallel to another wire carrying current in the same direction. What is the nature of the force between them?

Accepted Answer

They attract each other.

Question 12

Which law states that the total magnetic flux through any closed surface is zero?

Accepted Answer

Gauss's Law for Magnetism

Question 13

A circular loop of radius $$R$$ carries a current $$I. $$What is the magnetic field at the center of the loop?

Accepted Answer

$$B = \frac{\mu_0$ I}{2R}$$

Question 14

Which of the following best describes the path of a charged particle moving at an angle to a uniform magnetic field?

Accepted Answer

It follows a helical (spiral) path.

Question 15

Which of the following is NOT a property of magnetic field lines?

Accepted Answer

They can cross each other.

Question 16

A biomedical device uses ferromagnetic nanoparticles to target cancer cells. What is the main mechanism by which these nanoparticles help destroy cancer cells?

Accepted Answer

They generate local heat when exposed to an oscillating magnetic field, killing the cancer cells.

Question 17

Which of the following equations correctly expresses Ampere’s Law for the magnetic field around a closed loop?

Accepted Answer

$$\oint \vec{B} \cdot d\vec{l} = \mu_0$ I_{enc}$$

Question 18

A straight conductor of length $$L$$ carries a current $$I$$ and is placed in a uniform magnetic field $$B$$ perpendicular to the wire. What is the magnitude of the force on the wire?

Accepted Answer

$$F = I L B$$

Magnetism and Magnetic Fields: Principles and Biomedical Applications

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