Q: A wire segment of length $$\vec{l}$$ carries current $$I in a $$magnetic field $$\vec{B}. $$What is the vector expression for the force on the wire?

$$\vec{F} = I \vec{l} \times \vec{B}$$

Question 1

Which statement about magnetic field lines is correct?

Accepted Answer

Magnetic field lines form continuous, closed loops and never intersect.

Question 2

A charged particle moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the radius $$r of $$its circular path?

Accepted Answer

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

Question 3

Which of the following best explains why there are no magnetic monopoles?

Accepted Answer

Magnetic field lines form closed loops with no start or end points.

Question 4

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

Accepted Answer

$$F = ILB \sin 	heta$$

Question 5

Which law relates the magnetic field at a point to the sum of contributions from all current elements?

Accepted Answer

Biot-Savart Law

Question 6

Using Ampere’s Law, what is the magnetic field $$B at a $$distance $$r$$ from a long, straight wire carrying current $$I$$?

Accepted Answer

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

Question 7

A solenoid has $$n$$ turns per unit length and carries current $$I. $$What is the magnetic field inside the solenoid?

Accepted Answer

$$B = \mu_0$ n I$$

Question 8

A charged particle moves in a uniform magnetic field with velocity having both perpendicular and parallel components to $$\vec{B}. $$What is the resulting trajectory?

Accepted Answer

Helical path

Question 9

What is the direction of the magnetic field produced by a current-carrying straight wire?

Accepted Answer

In concentric circles around the wire, as given by the right-hand rule

Question 10

For a circular loop of radius $$R$$ carrying current $$I$$, what is the magnetic field at the center of the loop?

Accepted Answer

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

Question 11

Ampere’s Law in integral form is given by which equation?

Accepted Answer

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

Question 12

A toroid has $$N$$ windings and carries current $$I. $$What is the magnetic field inside the toroid at radius $$r$$?

Accepted Answer

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

Question 13

Which of the following is a correct application of the superposition principle for magnetic fields?

Accepted Answer

The total magnetic field at a point is the vector sum of the fields from each source.

Question 14

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

Accepted Answer

$$\vec{F} = I \vec{l} 	imes \vec{B}$$

Question 15

Which real-world phenomenon is best explained by the helical motion of charged particles in Earth's magnetic field?

Accepted Answer

The aurora borealis (northern lights)

Question 16

If the current in a solenoid is doubled, what happens to the magnetic field inside the solenoid?

Accepted Answer

It is doubled

Question 17

Which of the following statements about the Biot-Savart Law is correct?

Accepted Answer

It states that the magnetic field at a point is due to the vector sum of contributions from current elements.

Question 18

A long straight wire carries a current $$I. $$What is the direction of the magnetic field at a point located a distance $$r$$ from the wire?

Accepted Answer

In concentric circles around the wire, following the right-hand rule

Question 19

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

Accepted Answer

They can start or end at magnetic monopoles

LEC 3: Magnetic Field: Properties, Forces, and Laws (Electrodynamics & Relativity – Lecture 25)

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