Một quả cầu kim loại có khối lượng 0,2 g được treo trên một sợi dây cách điện được đặt trong một điện trường E có phương thẳng đứng, chiều từ dưới lên như hình vẽ. Cho biết gia tốc trọng trường g = 10 m/s^2. Nếu lực căng dây là 0,004 N, thì điện tích của quả cầu là:

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

elctricity and magnet is conversion to it

god i hope this !

the answer is c. the lower legs are levers, and the knees are fulcrums. the ankles hold the loads.