The density of seawater plays a vital role in causing ocean currents and circulating heat because of the fact that dense water sinks below less dense. long story short, seawater is the problem because its denser than pure water.
Maybe push or pull an object with a large amount of mass? you are force a (pushing through object) aka making contact. i hope i helped not good with physics :)
#16
If we put a resistor in circuit it will slow the speed of current
Let's check ohms law

- So if resistance is more current is less
#17
Again use ohms law


- Voltage must be increased