What is the SI unit of electric charge?

What is the sign of the charge carried by an electron?

An object gains \(5.0\times10^6\) electrons. Is its charge change positive or negative?

Find the charge of \(3.0\times10^8\) excess protons.

An object has net charge \(-8.0\,\mathrm{nC}\). Estimate how many excess electrons it has.

A neutral object loses \(1.2\times10^{10}\) electrons. Find its final charge.

Two isolated spheres have charges \(+12\,\mathrm{nC}\) and \(-5\,\mathrm{nC}\). They touch and are separated. If the final charge on sphere A is \(+4\,\mathrm{nC}\), find the final charge on sphere B.

A sample contains \(4.00\times10^{15}\) protons and \(4.00\times10^{15}+2.0\times10^7\) electrons. Find its net charge and sign.

Three isolated objects exchange charge. Initially their charges are \(Q_1,Q_2,Q_3\). After contact, objects 1 and 2 have final charges \(Q_1'=Q_1-a+b\) and \(Q_2'=Q_2+a-c\). Derive \(Q_3'\) from charge conservation and interpret the signs of \(a,b,c\).

A sensor claims it measured an isolated object's charge changing smoothly from \(0\) to \(0.50e\). Explain why this cannot be the final net charge of an ordinary isolated object, and state what assumption would have to fail for the claim to be meaningful.