1.Cells in the nervous system have a potential differenceof 70 mV across the cell membrane separating theinterior of the cell from the extracellular fluid. This potentialdifference is maintained by ion pumps that move charged ions acrossthe membrane.

Is this an emf? Select the correct answer and explanation.

1)No. The ion pumps cannot separate charges; thus, they cannotcreate a potential difference.
2)Yes. The ion pumps cannot separate charges, but they still cancreate a potential difference.
3)Yes. The ion pumps can actively separate charge; thus, they cancreate a potential difference.
4)No. The ion pumps can separate charges, but they cannot create apotential difference.

2.A 100 W lightbulb is brighter thana 60 W lightbulb when both operate at the samevoltage of 120 V.
If, instead, they were both operatedat the same current of 0.5 , which would bebrighter? Select the correct answer and explanation.

1)The 60 W bulb has a lower resistance, so it would bebrighter.
2)The 100 W bulb has a higher resistance, so it would bebrighter.
3)The 100 W bulb has a lower resistance, so it would bebrighter.
4)The 60 W bulb has a higher resistance, so it would bebrighter.

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1 The potential difference across the cell membrane maintained by ion pumps is not an emf Emf ... View the full answer