Is it permissible to purchase electrical appliances in installments from the workplace with an increase in price, and then sell them for profit?

Selling by installment is permissible if it is at a specific price known to both parties, not subject to increase even if payment is delayed. It does not matter if the price of the commodity by installment is higher than its price for immediate payment. If you buy the aforementioned devices and take possession of them, there is no harm in selling them at the price you desire.