Question
(a) A physicist performing a sensitive measurement wants to limit the magnetic force on a moving charge in her equipment to less than $1.00 \times 10^{-12} \textrm{ N}$. What is the greatest the charge can be if it moves at a maximum speed of 30.0 m/s in the Earth’s field? (b) Discuss whether it would be difficult to limit the charge to less than the value found in (a) by comparing it with typical static electricity and noting that static is often absent.
1. $6.7 \times 10^{-10} \textrm{ C}$
2. A typical static charge is about $1 \textrm{ }\mu\textrm{C}$ which is much greater than $6.7 \times 10^{-10} \textrm{ C}$. It will be difficult to isolate the experiment if static charge is around. However, it is possible to discharge the static charges in the vicinity, so it might be possible to isolate the experiment after all. Electronics manufacturing facilities have probably created systems and techniques for removing static charges that would otherwise affect their manufacturing processes.
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