Answer:
New force, 
Explanation:
The electrostatic force between two spheres is given by :

According to given condition, each of the spheres has lost half its initial charge, new force is given by :



So, the new force becomes (1/4)th of the initial force. Hence, the correct option is (d).
Answer:
The length of the wire is 83.2 m.
Explanation:
Given that,
Power of heater, P = 300 W
Voltage, V = 110 V
The resistivity of nichrome wire is, 
The electric power of a wire is given by :

Area of cross section of the wire is :

Resistance of a material is given by :

So, the length of the wire is 83.2 m. Hence, this is the required solution.
answer:
heating the material
placing the material in a magnetic field of opposite polarity
hitting the material
Answer:
For the first one its about 25 feet
Explanation: