1. A circuit must be a closed path in order for charge to flow. Therefore, there must be a conductor, that must form a connection from the voltage source to the electrical device and back. Without a conductor the electricity will have no path to flow out of the voltage source, pass the electrical device, and back to the voltage source.

2. A fuse's purpose is to shut off the circuit if there is to much current in it for safety purposes, because if there is to much current in it, the circuit could be overheated, and it might catch fire, or people might recieve an electric shock if part of the electricity might form a hole and flow outside where it is supposed to flow. So the me/tal strip that is put in a fuse must be melted just at the right time when it is overheated, because if it melts too easily for the device, using it would be very uncomfortable, and if it doesn't melt easily, even at a dangerous level, it will be of no use. So there must be a various type of fuses, because there are various types of electrical devices that needs different amounts of electricity, and users must know easily what fuse to use.

Q1. To connect the voltage source to the clectrical device and back.

Q2. A fuse is a thing that will break when overheated. So the fuse would have to be broken when it reaches a certain temperature.