Xét một solenoid có chiều dài rất lớn so với bề ngang. Trong số các cách dưới đây thì cách nào là hiệu quả nhất để tăng từ trường bên trong solenoid?

Acharge q experiences no net force at a particular point in space. which of the following situations described below must always be true? -there are no other charges nearby. -if there are other charges nearby, they must all have the same sign as q. -if there are other charges nearby, they must all have the opposite sign of q. -if there are other charges nearby, the total positive charge must equal the total negative charge. -none of the above