Questions: 3. Common static electricity involves charges ranging from nanocoulombs to microcoulombs. (a) How many electrons are needed to form a charge of -4.00 nC (b) How many electrons must be removed from a neutral object to leave a net charge of +0.2500 μC?

Solution Steps

• The charge of a single electron is \( e = -1.602 \times 10^{-19} \) coulombs.

• Given charge \( Q = -4.00 \) nanocoulombs (nC).
• Convert nanocoulombs to coulombs: \( Q = -4.00 \times 10^{-9} \) coulombs.
• Use the formula \( n = \frac{Q}{e} \) to find the number of electrons.
• \( n = \frac{-4.00 \times 10^{-9}}{-1.602 \times 10^{-19}} \).

• \( n \approx 2.50 \times 10^{10} \) electrons.

• Given charge \( Q = +0.2500 \) microcoulombs (μC).
• Convert microcoulombs to coulombs: \( Q = 0.2500 \times 10^{-6} \) coulombs.
• Use the formula \( n = \frac{Q}{e} \) to find the number of electrons.
• \( n = \frac{0.2500 \times 10^{-6}}{1.602 \times 10^{-19}} \).

• \( n \approx 1.56 \times 10^{12} \) electrons.

Final Answer