In many cases there will be more than one real-life 3D equivalent to the generic 2D views of parts. For example, a generic 2D battery can be represented by a AA, AAA, or PP3 battery in 3D.
To choose what type of real-life part you want the 3D view of a part to represent, select its Type in the part's Properties pane.
When selecting a new type, the part's value will automatically change to its real-life value. For example, when changing a battery from a pair of AA batteries to a PP3 battery, its voltage will automatically change to 9 V. Although a part may prefer a value that is allowed in real life, it will simulate with other values.