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# Electric Potential Question Watch

1. An oil droplet carrying a charge of +2e is in air between two parallel metal plates separated by a distance of 20mm. The pd between the plates is 5.0V.

Calculate the potential gradient between the two plates.

From what I know, Electric field strength = -(potential gradient)

But the answer states a positive value; 250.

Is this because of the positive charge of the oil droplet?
2. (Original post by Protoxylic)
An oil droplet carrying a charge of +2e is in air between two parallel metal plates separated by a distance of 20mm. The pd between the plates is 5.0V.

Calculate the potential gradient between the two plates.

From what I know, Electric field strength = -(potential gradient)

But the answer states a positive value; 250.

Is this because of the positive charge of the oil droplet?
The question simply states there is a potential difference of 5V between the plates. It does not state which plate has the higher potential. In the absence of this information, only the magnitude of the electric field is known and not the direction of the resulting force on the charged oil droplet. Hence the answer is unsigned.

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Updated: July 24, 2014
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