Calculate the net charge on a substance con-

sisting of a combination of 1.9 × 10^13 protons
and 3.9 × 10^13 electrons.
Answer in units of C.

To calculate the net charge on a substance, you need to find the difference between the total number of protons and electrons. Protons have a positive charge, while electrons have a negative charge. The unit of charge is Coulombs (C).

Given:
Number of protons = 1.9 × 10^13
Number of electrons = 3.9 × 10^13

Step 1: Determine the total positive charge from the protons.
Each proton carries a charge of +1.6 × 10^-19 C.
Total positive charge = Number of protons × Charge of one proton
= 1.9 × 10^13 × (1.6 × 10^-19 C)

Step 2: Determine the total negative charge from the electrons.
Each electron carries a charge of -1.6 × 10^-19 C.
Total negative charge = Number of electrons × Charge of one electron
= 3.9 × 10^13 × (-1.6 × 10^-19 C)

Step 3: Find the net charge by subtracting the total negative charge from the total positive charge.
Net charge = Total positive charge + Total negative charge

Perform the calculations:

Total positive charge = 1.9 × 10^13 × (1.6 × 10^-19 C)
= 3.04 × 10^-6 C

Total negative charge = 3.9 × 10^13 × (-1.6 × 10^-19 C)
= -6.24 × 10^-6 C

Net charge = 3.04 × 10^-6 C + (-6.24 × 10^-6 C)
= -3.2 × 10^-6 C

Therefore, the net charge on the substance is -3.2 × 10^-6 C.