State two differences between a primary cell and a secondary cell. State two characteristics of an electromotive force. Draw the electrical symbol for each of the following components of an electrical circuit: I. inductor; II. rheostat; III. diodes; IV. fuse.

Here are the electrical symbols for the remaining components:

• III. Diodes: The electrical symbol for a diode is an arrow pointing towards a bar, indicating the direction of conventional current flow.

  $$\boxed{\text{---}\blacktriangleright\text{|}\text{---}}$$

• IV. Fuse: The electrical symbol for a fuse is typically a rectangle with a line passing through it, or a curved line representing the melting element.

  $$\boxed{\text{---}\square\text{---}}$$