Answer:
The number of nails will be increased if more batteries are put in the circuit
The independent variable = The number of batteries
The dependent variable = The number of nails picked
Explanations:
Note:
The more the number of batteries used in the electromagnetic circuit, the higher the current flow, the higher the elctromagnetic effect.
Therefore, if the number of batteries is increased, the electromagnet will pick up more nails
Since the number of batteries used in the circuit is the input variable, it is considered as the independent variable
The number of nails picked is the output, hence it is the dependent variable.
That is, it deends on the number of batteries used