What condition must a point charge satisfy in order to produce a magnetic field?

State the magnetic field magnitude from a slowly moving point charge.

A positive charge moves to the right. At a point directly above the charge, is the magnetic field into or out of the page?

A charge \(3.0\times10^{-6}\,\mathrm C\) moves at \(2.0\times10^4\,\mathrm{m\,s^{-1}}\). Find \(B\) at a point \(0.30\,\mathrm m\) away, perpendicular to the velocity.

A positive charge moves so that the angle between \(\vec v\) and \(\vec r\) is \(30^\circ\). With \(q=4.0\times10^{-6}\,\mathrm C\), \(v=5.0\times10^4\,\mathrm{m\,s^{-1}}\), and \(r=0.20\,\mathrm m\), find \(B\).

Why is the magnetic field from a moving charge zero at a point directly in front of the charge's instantaneous velocity?

A negative charge moves to the right. At a point directly above it, is the magnetic field into or out of the page?

A charge \(+1.0\,\mathrm{nC}\) moves with \(\vec v=2.0\times10^5\hat\imath\,\mathrm{m\,s^{-1}}\). Find \(\vec B\) at a point \(0.10\,\mathrm m\) in the \(+y\) direction from the charge.

For the same moving charge and same angle \(\theta\), the speed is doubled and the field point is moved three times farther away. By what factor does \(B\) change?

A positive charge moves along the \(+x\)-axis. Compare the magnetic fields at points \((0,a,0)\) and \((0,0,a)\), both measured from the charge at the same instant.