4 Magnetism Free Online FlashCards

What happens to magnetic poles when a magnet is cut?

Magnetic field lines form continuous loops. Cutting a magnet produces smaller magnets, each with both a north and a south pole; isolated magnetic poles have not been observed.

When does a charge experience no magnetic force?

A stationary charge, or one moving parallel to the magnetic field, experiences no magnetic force.

How does magnetic force affect a particle’s speed and kinetic energy?

Magnetic force is perpendicular to a particle’s instantaneous motion, so it does no work. It can change the velocity’s direction, but not the particle’s speed or kinetic energy.

What path forms when velocity has parallel and perpendicular field components?

The velocity component perpendicular to the field causes circular motion, while the parallel component remains unchanged. Together they produce a helix around the field direction.

How do domains make a ferromagnetic material strongly magnetized?

Electrons have magnetic moments associated with intrinsic spin and orbital motion. In ferromagnets, groups of moments can align in domains; alignment of many domains makes the material strongly magnetized.

What do magnetic field-line direction and spacing represent?

The SI unit of magnetic field is the tesla (T). Field lines are tangent to the field, and closer spacing indicates a stronger field.

How do you find the magnetic-force direction on a moving charge?

For a positive charge, point your right-hand fingers along velocity and curl them toward the field; your thumb gives the force direction. Reverse that direction for a negative charge.

What determines the magnitude of magnetic force on a moving charge?

The force magnitude is $F_B=|q|vB\sin\theta$, where $\theta$ is the angle between the velocity and the field.

What force acts on a current-carrying wire in a magnetic field?

A straight current-carrying segment experiences $\mathbf{F}=I\,\mathbf{L}\times\mathbf{B}$, where $\mathbf{L}$ points in the direction of conventional current. This force is the operating principle behind electric motors.

What sets the radius of a charged particle’s circular path in a uniform field?

For motion perpendicular to a uniform field, the radius is $r=\frac{mv}{|q|B}$. Greater mass or speed widens the circle; a stronger field or larger charge magnitude tightens it.

What is the period of circular motion in a uniform magnetic field?

The circular-motion period is $T=\frac{2\pi m}{|q|B}$. It depends on the particle’s mass, charge magnitude, and field strength.

What magnetic field does a long straight current-carrying wire produce?

A long straight wire produces circular magnetic field lines around itself, with magnitude $B=\frac{\mu_0 I}{2\pi r}$. The right-hand grip rule gives the field direction.