Identify the variables in the investigation: An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different size nails were used. The number of paper clips the electromagnet could pick up was measured.

Independent: sizes of nails

Dependent: number of paper clips

Controlled: Battery, wire and type of nails

Explanation:

An independent variable is a variable which when changes does not the effect the results of the experiment. It does not depends upon the dependent variable.

A dependent variable is defined as a variable which is affected when the independent variable is changed by the researcher or the experimenter. It depends greatly upon the independent variable.

While a controlled variable is that variable whose value is not changed in an experiment. It contains all the constants.

In the context,

the independent variable are : sizes of nails

the dependent variables are : number of paper clips

the Controlled variables are: Battery, wire and type of nails

indium, and thallium have three electrons i think