I attach a voltage source to a 45 mF capacitor until it is fully charged. I then take the voltage source away and discharge the capacitor through a 120 Ω resistor in a basic RC circuit. If the initial current through the circuit during discharge is 0.5 A, what voltage did I apply to the capacitor to charge it?

60 V

Explanation:

Let the potential on capacitor be V . This will be equal to voltage of the source .

During discharge this voltage of capacitor will create current .

V / 120 = .5

V = 60 V

So this would have been the voltage of the source . So voltage of source

= 60 V

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

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide