Answer:
When one of charge is doubled, the magnitude of the force between them gets doubled.
Explanation:
The electric force between two electric charges is given by :

Here,
k is the electrostatic force
d is the separation between charges
are charges
If one of the charges is doubled in magnitude while maintaining the same separation between the charges, 
New force becomes,



When one of charge is doubled, the magnitude of the force between them gets doubled. Hence, this is the required solution.
Answer:
A.B = -38
Explanation:
A = 2i + 9j and B = -i - 4j.
So, A.B = (2i + 9j).(-i - 4j)
= 2i.(-i) + 2i.(-4j) + 9j.(-i) + 9j.(-4j)
= -2i.i - 8i.j - 9j.i - 36j.j
since i.i = 1, j.j = 1, i.j = 0 and j.i = 0, we have
A.B = -2(1) - 8(0) - 9(0) - 36(1)
A.B = -2 - 0 - 0 - 36
A.B = -38
Electric energy is transformed into mechanical energy of the dryer's engine and heat of the dryer's heater unit.
Answer:
No electromagnetic waves can not exists if changing magnetic field could produce electric fields but the changing electric fields could not produce magnetic fields. Electromagnetic waves are oscillating waves and they are based on this fact that the changing magnetic field produce electric field and the changing electric field produce the magnetic field. That is why these waves are known for self propagation and can even travel through vacuum. In this wave the electric field and the magnetic field lies perpendicular to each other. These waves travel with the speed of light and their example is light and other radiations coming from sun.