Final answer:
To give two metal spheres identical charges without touching them with the charged rod, you would use charging by induction, resulting in equal and opposite charges. When two charged spheres touch, the total charge redistributes evenly between them.
Step-by-step explanation:
Understanding Charging by Contact and Redistribution of Charge
To answer the student's original question, in order to give two metal spheres identical charges without touching them with a charged glass rod, you would use the method of charging by induction as explained in option d. This process involves bringing a charged rod near but not touching the first sphere, causing a separation of charges due to electrostatic force. Then, while the rod is still in place, separate the two spheres and remove the rod. This action results in both spheres retaining identical but opposite charges to that of the rod, without direct contact.
As for the additional question concerning two spheres with charges of –-5 nC and –-3 nC, when the spheres are brought together and touch, the total combined charge will redistribute evenly between them. Since the total charge is –-8 nC and there are two spheres, each sphere will end up with half of the total charge, resulting in both spheres having a charge of –-4 nC upon separation.