Question

$\text{Statement A :}$ A current carrying wire is placed parallel to the external magnetic field. The force on it due to the external magnetic field is zero.

$\text{Statement R :}$ The net charge on current wire is zero.

• A. Both $A$ and $R$ are true, and $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are true but $R$ is not correct explanation of $A$.
• C. $A$ is true, but $R$ is false.
• D. $A$ is false, but $R$ is true.

Answer 1

The correct option is B Both $A$ and $R$ are true but $R$ is not correct explanation of $A$.

Magnetic force on the current carrying conductor, $${\overrightarrow{F}}_B=(i\overrightarrow{l}\times \overrightarrow{B})$$ $\Rightarrow F_B=ilB\sin 0^{\circ }=0[\because \overrightarrow{l}||\overrightarrow{B}]$

$\therefore$ Statement $A$ is correct.

Due to the presence of equal number of electrons and protons inside a conductor, the net charge on the current wire would be zero.

So, statement $R$ is also correct but reason behind statement $A$ is ${\overrightarrow{F}}_B=(i\overrightarrow{l}\times \overrightarrow{B})\&\theta =0^{\circ }$

Hence, option (b) is the correct alternative.