Question

Which one of the following statement is true in case of current carrying conductor and a moving charge?

• A. Moving charge produces stronger electric field.
• B. Current carrying wire produces weaker magnetic field.
• C. Both current carrying wire and moving charge produce magnetic field at a point.
• D. Both repel each other with a greater force.

Answer 1

The correct option is C Both current carrying wire and moving charge produce magnetic field at a point.

The similarity between the current carrying conductor and a charge moving with a velocity $v$ is that, both produce the magnetic field around them. According to Biot-Savart's law, for the current carrying wire,

$dB=\frac{{\mu }_0}{4\pi }\frac{i(\underset{dl}{\to }\times \underset{r}{\to })}{|r{|}^3}$

While for a charge having charge $q$ and velocity $v$, $dB$ is given by,

$dB=\frac{{\mu }_0}{4\pi }\frac{q(\underset{v}{\to }\times \underset{r}{\to })}{|r{|}^3}$

So, the only difference is current and line element are getting replaced by charge and velocity.

Otherwise both represent the strength of the magnetic field at a point.