What type of substance is always made up of a single type of atom?

What kind of waves require a medium to travel? question 6 options: light waves mechanical waves all waves need a medium to travel electromagnetic waves

Aseries circuit contains a 30 e resistor, a 20 resistor, and a 10 resistor. the power supply provides 100 v to the circuit the current in the 10 resistor, to two significant figures, is a.

Aprotein molecule in an electrophoresis gel has a negative charge.the exact charge depends on the ph of the solution, but 30 excesselectrons is typical. what is the magnitude of the electric forceon a protein with this charge in a 1500 n/c electric field?