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