How to calculate the force between two electrified straight wire

all the goods sold by JD are genuine goods, and each order has its own "special invoice for goods" printed in Chinese (users of book goods are free to choose whether to issue an invoice). This invoice can be used as the reimbursement voucher of the company, and can be self drawn when placing an order

one package corresponds to one invoice. Different logistics centers issue different invoices for packages, and the invoice will be issued with each package

the invoice amount includes the delivery fee amount

set the invoice information method: click "modify" next to the invoice information on the order confirmation page to modify the invoice type (ordinary invoice, VAT invoice), invoice title (indivial, company), and invoice content (details, office supplies, computer accessories, consumables). The invoice title content cannot be empty. You can select the name of indivial or company. Content: in addition to digital procts, mobile phones and accessories, laptops, desktops and household appliances, the invoice content can select commodity details, office supplies, computer accessories and consumables. Only commodity details can be selected for VAT invoice content