Q: A charged particle moves through a region where both electric and magnetic fields are present. The total force on the particle is given by:

$$\vec{F} = q(\vec{E} + \vec{v} \times \vec{B})$$

Question 1

Which of the following statements best explains why a compass needle points north?

Accepted Answer

Because the north geographic pole of the Earth is a magnetic south pole.

Question 2

A charged particle with charge $$q$$ moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the magnitude of the magnetic force acting on the particle?

Accepted Answer

$$F = |q|vB$$

Question 3

Which of the following is true regarding magnetic monopoles?

Accepted Answer

There is no experimental evidence for their existence.

Question 4

A proton and an electron enter a uniform magnetic field with equal speeds and in the same direction. How do their paths compare?

Accepted Answer

They curve in opposite directions with the same radius.

Question 5

Which of the following best describes the direction of the magnetic force on a moving positive charge?

Accepted Answer

It is always perpendicular to both the velocity and the magnetic field vectors.

Question 6

A wire carries a current $$I in $$the presence of a uniform magnetic field $$\vec{B}. $$What is the expression for the magnetic force on a straight segment of length $$\ell$$?

Accepted Answer

$$F = I\ell B \sin 	heta$$

Question 7

Which of the following is the SI unit of magnetic flux?

Accepted Answer

Weber (Wb)

Question 8

A charged particle moves through a region where both electric and magnetic fields are present. The total force on the particle is given by:

Accepted Answer

$$\vec{F} = q(\vec{E} + \vec{v} 	imes \vec{B})$$

Question 9

Which of the following statements about magnetic field lines is correct?

Accepted Answer

They are tangent to the direction of the magnetic field at any point.

Question 10

A current loop of area $$A$$ and current $$I is $$placed in a uniform magnetic field $$B. $$What is the maximum torque experienced by the loop?

Accepted Answer

$$	au_{max} = IAB$$

Question 11

A particle of charge $$q$$ and mass $$m$$ moves with velocity $$v$$ perpendicular to a uniform magnetic field $$B. $$What is the radius $$r of $$its circular path?

Accepted Answer

$$r = \dfrac{mv}{qB}$$

Question 12

Which of the following best describes the potential energy $$U of a $$magnetic dipole moment $$\vec{\mu} in a $$magnetic field $$\vec{B}$$?

Accepted Answer

$$U = -\vec{\mu} \cdot \vec{B}$$

Question 13

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

$$v = E/B$$

Question 14

Which of the following is NOT a property of the magnetic force on a moving charge?

Accepted Answer

It acts on a stationary charge.

Question 15

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

Accepted Answer

$$F = I\ell B$$

Question 16

Which of the following best describes the motion of a charged particle in a uniform magnetic field if its velocity is not perpendicular to the field?

Accepted Answer

It moves in a helical path.

Question 17

The SI unit of magnetic field $$B is $$the tesla (T). Which of the following is equivalent to 1 tesla?

Accepted Answer

$$1\,\mathrm{T} = 1\,\mathrm{N}/(\mathrm{A} \cdot \mathrm{m})$$

Question 18

Which of the following is true about the net force on a current loop in a uniform magnetic field?

Accepted Answer

It is always zero.

Question 19

A bar magnet is cut in half. What happens to the magnetic poles?

Accepted Answer

Each half has both a north and a south pole.

Question 20

Which of the following best describes the relationship between magnetic field lines and the force on a charged particle?

Accepted Answer

The force is always perpendicular to both the velocity and the field lines.

Magnetic Field and Magnetic Forces – Chapter 27 Study Notes

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